Exhibit 99.1 J.P. Morgan Healthcare Conference January 11, 2021Exhibit 99.1 J.P. Morgan Healthcare Conference January 11, 2021

Safe Harbor Certain statements in this presentation and the accompanying oral commentary are forward-looking statements within the meaning of federal securities laws. These statements relate to future events or Guardant Health, Inc. (the “Company”)’s future results and involve known and unknown risks, uncertainties and other factors that may cause the actual results, levels of activity, performance or achievements of the Company or its industry to be materially different from those expressed or implied by any forward-looking statements. In some cases, forward-looking statements can be identified by terminology such as “may,” “will,” “could,” “would,” “should,” “to,” “target,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “potential” or other comparable terminology. All statements other than statements of historical fact could be deemed forward-looking, including any expectations regarding the Company's commercial engine as a force multiplier for research and development initiatives; any projections of market opportunities or any statements regarding expectations for future reimbursement opportunities; statements regarding the Company’s long-term expectations, including with respect to oncology, liquid biopsy, and other aspects of the Company’s industry; statements about launching planned new products and additional laboratories, including with respect to Guardant Reveal, CGP tissue assay, and laboratories outside the United States; statements about the number of patients and clinical sites targeted for, as well as the expected completion of, the Company’s ECLIPSE trial; any statements regarding expectations for future regulatory approvals; any statements about historical results that may suggest trends for the Company’s business; any statements of the plans, strategies, and objectives of management for future operations and directions; any statements of expectation or belief regarding future events, opportunities to drive future growth, potential markets or market size, or technology developments; and any statements of assumptions underlying any of the items mentioned. The Company has based these forward-looking statements on its current expectations, assumptions, estimates and projections. While the Company believes these expectations, assumptions, estimates and projections are reasonable, such forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond the Company's control. These and other important factors may cause actual results, performance or achievements to differ materially from those expressed or implied by these forward-looking statements. The forward-looking statements in this presentation are made only as of the date hereof. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the Company in general, see the Company's periodic filings with the Securities and Exchange Commission (the SEC ), including its Annual Report on Form 10-K for the year ended December 31, 2019, its Quarterly Reports on Form 10-Q for the periods ended March 31, 2020, June 30, 2020, and September 30, 2020, respectively, and any current and periodic reports filed thereafter. Except as required by law, the Company assumes no obligation and does not intend to update these forward-looking statements or to conform these statements to actual results or to changes in the Company's expectations. This presentation also contains estimates and other statistical data made by independent parties and by the Company relating to market size, penetration and growth and other data about the Company's industry, which involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions, and estimates of the Company's future performance and the future performance of the markets in which the Company operates are necessarily subject to a high degree of uncertainty and risk. In light of the foregoing, investors are urged not to rely on any forward-looking statement or third-party data in reaching any conclusion or making any investment decision about any securities of the Company. 2Safe Harbor Certain statements in this presentation and the accompanying oral commentary are forward-looking statements within the meaning of federal securities laws. These statements relate to future events or Guardant Health, Inc. (the “Company”)’s future results and involve known and unknown risks, uncertainties and other factors that may cause the actual results, levels of activity, performance or achievements of the Company or its industry to be materially different from those expressed or implied by any forward-looking statements. In some cases, forward-looking statements can be identified by terminology such as “may,” “will,” “could,” “would,” “should,” “to,” “target,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “potential” or other comparable terminology. All statements other than statements of historical fact could be deemed forward-looking, including any expectations regarding the Company's commercial engine as a force multiplier for research and development initiatives; any projections of market opportunities or any statements regarding expectations for future reimbursement opportunities; statements regarding the Company’s long-term expectations, including with respect to oncology, liquid biopsy, and other aspects of the Company’s industry; statements about launching planned new products and additional laboratories, including with respect to Guardant Reveal, CGP tissue assay, and laboratories outside the United States; statements about the number of patients and clinical sites targeted for, as well as the expected completion of, the Company’s ECLIPSE trial; any statements regarding expectations for future regulatory approvals; any statements about historical results that may suggest trends for the Company’s business; any statements of the plans, strategies, and objectives of management for future operations and directions; any statements of expectation or belief regarding future events, opportunities to drive future growth, potential markets or market size, or technology developments; and any statements of assumptions underlying any of the items mentioned. The Company has based these forward-looking statements on its current expectations, assumptions, estimates and projections. While the Company believes these expectations, assumptions, estimates and projections are reasonable, such forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond the Company's control. These and other important factors may cause actual results, performance or achievements to differ materially from those expressed or implied by these forward-looking statements. The forward-looking statements in this presentation are made only as of the date hereof. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the Company in general, see the Company's periodic filings with the Securities and Exchange Commission (the SEC ), including its Annual Report on Form 10-K for the year ended December 31, 2019, its Quarterly Reports on Form 10-Q for the periods ended March 31, 2020, June 30, 2020, and September 30, 2020, respectively, and any current and periodic reports filed thereafter. Except as required by law, the Company assumes no obligation and does not intend to update these forward-looking statements or to conform these statements to actual results or to changes in the Company's expectations. This presentation also contains estimates and other statistical data made by independent parties and by the Company relating to market size, penetration and growth and other data about the Company's industry, which involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions, and estimates of the Company's future performance and the future performance of the markets in which the Company operates are necessarily subject to a high degree of uncertainty and risk. In light of the foregoing, investors are urged not to rely on any forward-looking statement or third-party data in reaching any conclusion or making any investment decision about any securities of the Company. 2

Delivering the promise of precision oncology across the continuum of care Therapy Selection Recurrence Monitoring ScreeningDelivering the promise of precision oncology across the continuum of care Therapy Selection Recurrence Monitoring Screening

Informing treatment at all stages of disease progression JUL-27-2018 FEB-20-2020 JUL-16-2020 AUG-27-2020 OCT-26-2020 EGFR E746_A750del (Exon 19 deletion) TP53 S127F EGFR C797S ARID1A Q456Q NTRK2 L699L Highest Variant EGFR N338N Allele Fraction i 41.2% 0.3% 5.2% 58.3% 0.2% Amplifications not graphed Star Dolbier. In 2018 osimertinib erlotinib diagnosed with Stage IV NSCLC “A simple blood test has saved my life.” Therapy Selection – StarInforming treatment at all stages of disease progression JUL-27-2018 FEB-20-2020 JUL-16-2020 AUG-27-2020 OCT-26-2020 EGFR E746_A750del (Exon 19 deletion) TP53 S127F EGFR C797S ARID1A Q456Q NTRK2 L699L Highest Variant EGFR N338N Allele Fraction i 41.2% 0.3% 5.2% 58.3% 0.2% Amplifications not graphed Star Dolbier. In 2018 osimertinib erlotinib diagnosed with Stage IV NSCLC “A simple blood test has saved my life.” Therapy Selection – Star

Guardant Health Liquid Biopsy Platform 1 Poised to transform cancer management and unlock $70B+ U.S. market opportunity Recurrence Therapy Early Cancer Monitoring Selection Screening 2 ~700K Advanced cancer patients ~15M Early-stage survivors 100M+ Individuals • Comprehensive genomic profiling • Neoadjuvant/adjuvant treatment • Early-stage cancer detection • Molecular tumor evolution • Minimal residual disease detection • Treatment resistance • Recurrence monitoring $50B • With multi-cancer screening Biopharma opportunities $20B Molecular response & monitoring $15B • Average-risk CRC $6B 1. U.S. Market Opportunity (estimate). Sources: CDC Statistics; US Census; American Cancer Society Cancer Facts and Statistics; SEER; Rebecca L. Siegel, Cancer Statistics, 2018, A Cancer Journal for Clinicals, 68:7; Piper Jaffray, Liquid Biopsy Report, Cowen Equity Research, Foundation Medicine, dated March 18, 2018; CDC, Viral Hepatitis and Liver Cancer report. Note: Market sizing based on Guardant Health internal analysis. 2. Asymptomatic, high-risk individuals 5Guardant Health Liquid Biopsy Platform 1 Poised to transform cancer management and unlock $70B+ U.S. market opportunity Recurrence Therapy Early Cancer Monitoring Selection Screening 2 ~700K Advanced cancer patients ~15M Early-stage survivors 100M+ Individuals • Comprehensive genomic profiling • Neoadjuvant/adjuvant treatment • Early-stage cancer detection • Molecular tumor evolution • Minimal residual disease detection • Treatment resistance • Recurrence monitoring $50B • With multi-cancer screening Biopharma opportunities $20B Molecular response & monitoring $15B • Average-risk CRC $6B 1. U.S. Market Opportunity (estimate). Sources: CDC Statistics; US Census; American Cancer Society Cancer Facts and Statistics; SEER; Rebecca L. Siegel, Cancer Statistics, 2018, A Cancer Journal for Clinicals, 68:7; Piper Jaffray, Liquid Biopsy Report, Cowen Equity Research, Foundation Medicine, dated March 18, 2018; CDC, Viral Hepatitis and Liver Cancer report. Note: Market sizing based on Guardant Health internal analysis. 2. Asymptomatic, high-risk individuals 5

Guardant Health Liquid Biopsy Platform Unlocks multiple dimensions of cancer signals in blood Somatic Alterations Methylation Fragmentomics Proprietary High- Next-Generation AI-Powered Conversion Biochemistry Sequencing Bioinformatics CCGA 2 – 3x 1000x TAGAT higher conversion reduction in sequencing AGA efficiency AC error rate PATENTED DIGITAL SEQUENCING PLATFORM Source: Guardant Health Data on File. Odegaard J, et al. CCR 2018 6Guardant Health Liquid Biopsy Platform Unlocks multiple dimensions of cancer signals in blood Somatic Alterations Methylation Fragmentomics Proprietary High- Next-Generation AI-Powered Conversion Biochemistry Sequencing Bioinformatics CCGA 2 – 3x 1000x TAGAT higher conversion reduction in sequencing AGA efficiency AC error rate PATENTED DIGITAL SEQUENCING PLATFORM Source: Guardant Health Data on File. Odegaard J, et al. CCR 2018 6

Therapy SelectionTherapy Selection

Comprehensive Liquid Biopsy Platform for Oncologists 2 1 First comprehensive liquid biopsy Next-generation to receive FDA approval liquid biopsy assay Approved for genomic profiling across Higher performance all advanced solid tumors Additional HRD genes Approved as a companion diagnostic for osimertinib Coverage for NTRK2 and NTRK3 fusions Average TAT of 5–7 days Tumor mutational burden (TMB) score 8Comprehensive Liquid Biopsy Platform for Oncologists 2 1 First comprehensive liquid biopsy Next-generation to receive FDA approval liquid biopsy assay Approved for genomic profiling across Higher performance all advanced solid tumors Additional HRD genes Approved as a companion diagnostic for osimertinib Coverage for NTRK2 and NTRK3 fusions Average TAT of 5–7 days Tumor mutational burden (TMB) score 8

Realizing Liquid Biopsy Market Opportunity Requires Significantly More Than Technology $6B 2 U.S. Opportunity Operations & Reimbursement Commercial Regulatory Infrastructure • 200M+ Clinical Approval covered lives • 9,000+ Evidence oncologists • FDA approval • Medicare • 60+ pan-cancer • 60+ • CDx 1 outcome studies coverage biopharma collaborations partners • 200 publications Best-in-class technology 1. Covers all solid tumor cancers except tumors primary to the central nervous system such as brain cancers. 2. U.S. Market Opportunity (estimate); Source: CDC Statistics; US Census; American Cancer Society Cancer Facts and Statistics; SEER; Rebecca L. Siegel, Cancer Statistics, 2018, A Cancer Journal for Clinicals, 68:7; Piper Jaffray, Liquid Biopsy Report, Cowen Equity Research, Foundation Medicine, dated March 18, 2018; CDC, Viral Hepatitis and Liver Cancer report. Note: Market sizing based on Guardant Health internal analysis 9Realizing Liquid Biopsy Market Opportunity Requires Significantly More Than Technology $6B 2 U.S. Opportunity Operations & Reimbursement Commercial Regulatory Infrastructure • 200M+ Clinical Approval covered lives • 9,000+ Evidence oncologists • FDA approval • Medicare • 60+ pan-cancer • 60+ • CDx 1 outcome studies coverage biopharma collaborations partners • 200 publications Best-in-class technology 1. Covers all solid tumor cancers except tumors primary to the central nervous system such as brain cancers. 2. U.S. Market Opportunity (estimate); Source: CDC Statistics; US Census; American Cancer Society Cancer Facts and Statistics; SEER; Rebecca L. Siegel, Cancer Statistics, 2018, A Cancer Journal for Clinicals, 68:7; Piper Jaffray, Liquid Biopsy Report, Cowen Equity Research, Foundation Medicine, dated March 18, 2018; CDC, Viral Hepatitis and Liver Cancer report. Note: Market sizing based on Guardant Health internal analysis 9

Strong Clinical Adoption Test Volume +28% +60% 16,950 +15% 15,257 13,694 13,259 11,875 9,521 Q1 19 Q1 20 Q2 19 Q2 20 Q3 19 Q3 20 10Strong Clinical Adoption Test Volume +28% +60% 16,950 +15% 15,257 13,694 13,259 11,875 9,521 Q1 19 Q1 20 Q2 19 Q2 20 Q3 19 Q3 20 10

Still Early Innings of Adoption in the Advanced Cancer Market U.S. Test Volume Guardant Penetration 1 of U.S. Market All Other ~4% Colorectal ~5% Breast ~8% Genitourinary ~12% Lung ~13% Q3 20 1. Opportunity is estimated using Kantar’s Patient Metrics and Tx Architecture for 1L treated patients and patients receiving drug therapy at later lines. Data from January 1, 2020 – September 30, 2020 11Still Early Innings of Adoption in the Advanced Cancer Market U.S. Test Volume Guardant Penetration 1 of U.S. Market All Other ~4% Colorectal ~5% Breast ~8% Genitourinary ~12% Lung ~13% Q3 20 1. Opportunity is estimated using Kantar’s Patient Metrics and Tx Architecture for 1L treated patients and patients receiving drug therapy at later lines. Data from January 1, 2020 – September 30, 2020 11

Expanding Clinical Utility of Guardant360 Tumor Molecular Longitudinal Profiling Response Monitoring Use of ctDNA testing at Assess changes in ctDNA during Assess +/- of ctDNA over time diagnosis & progression treatment 2–9 wks. vs. baseline 200 40+ 10+ Total Publications of total pubs of total pubs • Rapid, non-invasive CGP • Predicts PFS & OS after immunotherapy • Superior to many protein-based or targeted therapy biomarkers • Identifies actionable targets & acquired therapy resistance • ctDNA clearance after immunotherapy • ctDNA changes precede can help differentiate eventual benefit radiologic changes by 6–12 weeks vs. radiography at 6–9 weeks Note: Guardant Health data on file 12Expanding Clinical Utility of Guardant360 Tumor Molecular Longitudinal Profiling Response Monitoring Use of ctDNA testing at Assess changes in ctDNA during Assess +/- of ctDNA over time diagnosis & progression treatment 2–9 wks. vs. baseline 200 40+ 10+ Total Publications of total pubs of total pubs • Rapid, non-invasive CGP • Predicts PFS & OS after immunotherapy • Superior to many protein-based or targeted therapy biomarkers • Identifies actionable targets & acquired therapy resistance • ctDNA clearance after immunotherapy • ctDNA changes precede can help differentiate eventual benefit radiologic changes by 6–12 weeks vs. radiography at 6–9 weeks Note: Guardant Health data on file 12

Guardant360 Molecular Response Predicts responders on-average 8 weeks earlier than RECIST Robust molecular response data across various treatments and indications PFS (months) Progression Free Survival (PFS) Indication Therapy (ctDNA decreased vs. increased) Pembroluzimab 1 Bladder durvalumab 13.8 vs. 1.6 Durvalumab 1 Afatinib NSCLC durvalumab 13.7 vs. 1.45 Lorlatinib 2 NSCLC pembrolizumab HR = 0.24 (p=0.017) 0 2 4 6 8 10 12 14 16 3 Gastric pembrolizumab 4.0 vs. 2.2 Molecular responders Molecular non-responders 4 NSCLC lorlatinib 6.6 vs. 2.6 100 - Molecular non-responder 5 Breast Multiple 7.3 vs. 2.3 (HR=3.44) Molecular responder 70 - 6 NSCLC afatinib 15.1 vs. 2.8 (p=0.0009) 50 - 7 Gastric pembrolizumab + trastuzumab 12.3 vs. 3.9 20 - 8 0 - Breast trastuzumab deruxtecan 18.1 vs. 6.2 0 6 12 18 24 30 9 Months 1. Raja (Ranade) et al 2018 Clinical Cancer Research; 2. Aggarwal (Carpenter) et al ASCO 2019 JCO 37, no.15; 3. Kim (Kang) et al. 2018 Nat Med; 4. Shaw (Solomon) et al ASCO 2019 JCO 37, no.15; 5. Pascual (Turner (et al) 2020 SABCS 2020 6. Mack (Gandara) et al. 2020 J Clin Oncol 38; 7. Maron (Janjigian) et al. 2020 J Clin Oncol 38; 8. Modi (Park) et al. 2020 J Clin Oncol 38; 9. Zhang (Hellman) et al. 2020 Cancer Discovery 13 PFS Probability (%)Guardant360 Molecular Response Predicts responders on-average 8 weeks earlier than RECIST Robust molecular response data across various treatments and indications PFS (months) Progression Free Survival (PFS) Indication Therapy (ctDNA decreased vs. increased) Pembroluzimab 1 Bladder durvalumab 13.8 vs. 1.6 Durvalumab 1 Afatinib NSCLC durvalumab 13.7 vs. 1.45 Lorlatinib 2 NSCLC pembrolizumab HR = 0.24 (p=0.017) 0 2 4 6 8 10 12 14 16 3 Gastric pembrolizumab 4.0 vs. 2.2 Molecular responders Molecular non-responders 4 NSCLC lorlatinib 6.6 vs. 2.6 100 - Molecular non-responder 5 Breast Multiple 7.3 vs. 2.3 (HR=3.44) Molecular responder 70 - 6 NSCLC afatinib 15.1 vs. 2.8 (p=0.0009) 50 - 7 Gastric pembrolizumab + trastuzumab 12.3 vs. 3.9 20 - 8 0 - Breast trastuzumab deruxtecan 18.1 vs. 6.2 0 6 12 18 24 30 9 Months 1. Raja (Ranade) et al 2018 Clinical Cancer Research; 2. Aggarwal (Carpenter) et al ASCO 2019 JCO 37, no.15; 3. Kim (Kang) et al. 2018 Nat Med; 4. Shaw (Solomon) et al ASCO 2019 JCO 37, no.15; 5. Pascual (Turner (et al) 2020 SABCS 2020 6. Mack (Gandara) et al. 2020 J Clin Oncol 38; 7. Maron (Janjigian) et al. 2020 J Clin Oncol 38; 8. Modi (Park) et al. 2020 J Clin Oncol 38; 9. Zhang (Hellman) et al. 2020 Cancer Discovery 13 PFS Probability (%)

Comprehensive Product Offerings for Oncologists 1 2 3 Tissue Existing Challenges 1st Comprehensive Liquid Biopsy Next-Generation to Receive FDA Approval Liquid Biopsy Assay Misses ~15–20% of actionable Industry-leading liquid biopsy Comprehensive, high- alterations performance assay 1 Most validated liquid biopsy Industry-leading blood-based Average TAT of 21–28 days Average TAT of 5–7 days TMB assessment Challenging specimens/input Approved across all solid amounts tumors 1. Data on file 14Comprehensive Product Offerings for Oncologists 1 2 3 Tissue Existing Challenges 1st Comprehensive Liquid Biopsy Next-Generation to Receive FDA Approval Liquid Biopsy Assay Misses ~15–20% of actionable Industry-leading liquid biopsy Comprehensive, high- alterations performance assay 1 Most validated liquid biopsy Industry-leading blood-based Average TAT of 21–28 days Average TAT of 5–7 days TMB assessment Challenging specimens/input Approved across all solid amounts tumors 1. Data on file 14

Comprehensive Product Offerings for Oncologists 1 2 3 Coming Soon in 2021 Next-Generation 1st Comprehensive Liquid Biopsy Next-Generation to Receive FDA Approval Liquid Biopsy Assay Tissue Assay Industry-leading liquid biopsy Comprehensive, high- Expected to address current performance assay challenges with tissue testing 1 Most validated liquid biopsy Industry-leading blood-based Average TAT of 5–7 days CGP for all solid-tumors, TMB assessment including guideline- Approved across all solid recommended biomarkers, tumors TMB, HRD and MSI 1. Data on file 15Comprehensive Product Offerings for Oncologists 1 2 3 Coming Soon in 2021 Next-Generation 1st Comprehensive Liquid Biopsy Next-Generation to Receive FDA Approval Liquid Biopsy Assay Tissue Assay Industry-leading liquid biopsy Comprehensive, high- Expected to address current performance assay challenges with tissue testing 1 Most validated liquid biopsy Industry-leading blood-based Average TAT of 5–7 days CGP for all solid-tumors, TMB assessment including guideline- Approved across all solid recommended biomarkers, tumors TMB, HRD and MSI 1. Data on file 15

Recurrence MonitoringRecurrence Monitoring

LUNAR-1 CRC Data Demonstrates Industry-Leading Performance in the Detection of Minimal Residual Disease 1 Without Need for Tissue Biopsy For recurrence detection with 91% surveillance samples Sensitivity For recurrence detection following 100% completion of definitive therapy Specificity Methylation Somatic Alterations Differential methylation in SNVs and Indels normal vs. tumor DNA Integration of genomic and epigenomic ctDNA signals increased sensitivity by 36% 1. Parikh (Corcoran) ESMO 2020, manuscript under review 17LUNAR-1 CRC Data Demonstrates Industry-Leading Performance in the Detection of Minimal Residual Disease 1 Without Need for Tissue Biopsy For recurrence detection with 91% surveillance samples Sensitivity For recurrence detection following 100% completion of definitive therapy Specificity Methylation Somatic Alterations Differential methylation in SNVs and Indels normal vs. tumor DNA Integration of genomic and epigenomic ctDNA signals increased sensitivity by 36% 1. Parikh (Corcoran) ESMO 2020, manuscript under review 17

Three Interventional LUNAR-1 Trials Launched in 2020 ACT-3 PEGASUS COBRA Escalation Trial De-Escalation Trial Escalation Trial • ~1,400 resectable stage II colon • 500 stage III colorectal cancer • 140 high-risk colon cancer patients cancer patients suitable for active patients after complete surgical after surgical resection surveillance resection & standard adjuvant • T4N0 stage II & stage III chemotherapy (microsatellite stable) 18Three Interventional LUNAR-1 Trials Launched in 2020 ACT-3 PEGASUS COBRA Escalation Trial De-Escalation Trial Escalation Trial • ~1,400 resectable stage II colon • 500 stage III colorectal cancer • 140 high-risk colon cancer patients cancer patients suitable for active patients after complete surgical after surgical resection surveillance resection & standard adjuvant • T4N0 stage II & stage III chemotherapy (microsatellite stable) 18

Launching in Q1 2021 The FIRST blood-only liquid biopsy for residual disease detection and recurrence monitoring 7 days Early-stage Plasma only Industry-leading Additional 1 colorectal ctDNA test sensitivity cancer types cancer is with industry- to follow the first leading TAT indication 1. Due to simultaneous interrogation of genomic and methylation signals 19Launching in Q1 2021 The FIRST blood-only liquid biopsy for residual disease detection and recurrence monitoring 7 days Early-stage Plasma only Industry-leading Additional 1 colorectal ctDNA test sensitivity cancer types cancer is with industry- to follow the first leading TAT indication 1. Due to simultaneous interrogation of genomic and methylation signals 19

Early Cancer ScreeningEarly Cancer Screening

Screening Compliance Rates in CRC Represents a Significant Unmet Need % of U.S. adults age 50+ 1 up to date with CRC screening #2 Cause of cancer deaths 80% CDC GOAL 68.8% 67.3% 66.2% 65.2% 1in 3 Adults age 50+ not screened as recommended Age <50 incidence is growing 2012 2014 2016 2018 1. Nov 2019 NCCRT Annual Meeting, presented by Richard Wender Chief Cancer Control Officer ACS. Data based on Behavioral Risk Factor Surveillance System Survey 21Screening Compliance Rates in CRC Represents a Significant Unmet Need % of U.S. adults age 50+ 1 up to date with CRC screening #2 Cause of cancer deaths 80% CDC GOAL 68.8% 67.3% 66.2% 65.2% 1in 3 Adults age 50+ not screened as recommended Age <50 incidence is growing 2012 2014 2016 2018 1. Nov 2019 NCCRT Annual Meeting, presented by Richard Wender Chief Cancer Control Officer ACS. Data based on Behavioral Risk Factor Surveillance System Survey 21

LUNAR-2 Assay Shows High Sensitivity in Detecting CRC 1 Epigenomic signatures improve sensitivity 97% 90% Epi+ Genomic Genomic Somatic Specificity Sensitivity Methylation Fragmentomics Alterations 88 cancer-free 113 recently age-matched diagnosed colorectal cancer patients cohorts 1. O. Westesson et al. 2019. American Association for Cancer Research Annual Meeting. Abstract #916 22LUNAR-2 Assay Shows High Sensitivity in Detecting CRC 1 Epigenomic signatures improve sensitivity 97% 90% Epi+ Genomic Genomic Somatic Specificity Sensitivity Methylation Fragmentomics Alterations 88 cancer-free 113 recently age-matched diagnosed colorectal cancer patients cohorts 1. O. Westesson et al. 2019. American Association for Cancer Research Annual Meeting. Abstract #916 22

ECLIPSE: Enrollment on Track for Completion in 2021 Regulatory grade study has the potential for enabling FDA approval & CMS coverage LUNAR-2 Blood Test VS Screening Colonoscopy Evaluating performance of LUNAR-2 to detect CRC in average-risk adults Prospective ~10,000 150+ U.S. Trial Individuals Target Sites • Average risk for CRC • Age 45–84 1. ClinicalTrials.gov Identifier: NCT04136002 23ECLIPSE: Enrollment on Track for Completion in 2021 Regulatory grade study has the potential for enabling FDA approval & CMS coverage LUNAR-2 Blood Test VS Screening Colonoscopy Evaluating performance of LUNAR-2 to detect CRC in average-risk adults Prospective ~10,000 150+ U.S. Trial Individuals Target Sites • Average risk for CRC • Age 45–84 1. ClinicalTrials.gov Identifier: NCT04136002 23

BiopharmaBiopharma

$2B Biopharma Opportunity 1,200+ Retrospective Trials Targeted therapy and I-O programs 17% Prospective CDx Trials 130,000+ 15% 56% Patients Commercial 12% 60+ Pharma partners 1 $2 billion of the $6 billion therapy selection market 1. U.S. Market Opportunity (estimate). Sources: SEER; Rebecca L. Siegel, Cancer Statistics, 2018, A Cancer Journal for Clinicians, 68:7; Piper Jaffray, Liquid Biopsy Report. Guardant Health 25 Biopharma, Global Data, June 2017; clinicaltrials.gov; Campbell (Meyerson) and TCGA 2016 Nature Genetics. Note: Market sizing based on Guardant Health internal analysis$2B Biopharma Opportunity 1,200+ Retrospective Trials Targeted therapy and I-O programs 17% Prospective CDx Trials 130,000+ 15% 56% Patients Commercial 12% 60+ Pharma partners 1 $2 billion of the $6 billion therapy selection market 1. U.S. Market Opportunity (estimate). Sources: SEER; Rebecca L. Siegel, Cancer Statistics, 2018, A Cancer Journal for Clinicians, 68:7; Piper Jaffray, Liquid Biopsy Report. Guardant Health 25 Biopharma, Global Data, June 2017; clinicaltrials.gov; Campbell (Meyerson) and TCGA 2016 Nature Genetics. Note: Market sizing based on Guardant Health internal analysis

Guardant360 Liquid Biopsy Accelerates clinical trial enrollment compared to tissue biopsy Guardant360 GOZILA ctDNA VS GI-SCREEN Tissue • 3X faster time to screening result (11 vs 33 days) • 2.3X improved enrollment rate (9.5% vs 4.1%) • Similar ORR & PFS Source: Nakamura, Y., Taniguchi, H., Ikeda, M. et al. Clinical utility of circulating tumor DNA sequencing in advanced gastrointestinal cancer: SCRUM-Japan GI-SCREEN and GOZILA studies. Nat Medicine (2020). https://doi.org/10.1038/s41591-020-1063-5 26Guardant360 Liquid Biopsy Accelerates clinical trial enrollment compared to tissue biopsy Guardant360 GOZILA ctDNA VS GI-SCREEN Tissue • 3X faster time to screening result (11 vs 33 days) • 2.3X improved enrollment rate (9.5% vs 4.1%) • Similar ORR & PFS Source: Nakamura, Y., Taniguchi, H., Ikeda, M. et al. Clinical utility of circulating tumor DNA sequencing in advanced gastrointestinal cancer: SCRUM-Japan GI-SCREEN and GOZILA studies. Nat Medicine (2020). https://doi.org/10.1038/s41591-020-1063-5 26

Pipeline of Announced Guardant360 CDx Indications Approved Supplemental Supplemental CDx PMA Submitted PMA Submitted Osimertinib Amivantamab Sotorasib Elacestrant 27Pipeline of Announced Guardant360 CDx Indications Approved Supplemental Supplemental CDx PMA Submitted PMA Submitted Osimertinib Amivantamab Sotorasib Elacestrant 27

GuardantINFORM Accelerates development of next-generation cancer therapeutics Patient Database with Integrated Clinical 135K+ and Molecular Information 60+ 2,400+ 6,000+ 15,000+ Cancer Types Distinct Cancer Distinct Cancer- Patients with >1 Treatments Related Procedures G360 Test Targeted Drug Development Clinical Trial Optimization Post-Marketing Studies Note: Guardant Health data on file 28GuardantINFORM Accelerates development of next-generation cancer therapeutics Patient Database with Integrated Clinical 135K+ and Molecular Information 60+ 2,400+ 6,000+ 15,000+ Cancer Types Distinct Cancer Distinct Cancer- Patients with >1 Treatments Related Procedures G360 Test Targeted Drug Development Clinical Trial Optimization Post-Marketing Studies Note: Guardant Health data on file 28

InternationalInternational

Increasing Global Access to Our Liquid Biopsy Platform • European partner laboratory planned for 2021 at Vall d’Hebron Institute of Oncology, Barcelona • Guardant360 CDx CE Marked, ISO-13485 Certified Europe & ISO-15189 Accredited • 10,000+ patients tested • Guardant360 PMDA submission planned for 1H 2021 Asia • Guardant360 tests available in 40+ countries AMEA Middle East • 1,500+ prescribing oncologists Africa • Japan laboratory expected to be operational in 2021 30Increasing Global Access to Our Liquid Biopsy Platform • European partner laboratory planned for 2021 at Vall d’Hebron Institute of Oncology, Barcelona • Guardant360 CDx CE Marked, ISO-13485 Certified Europe & ISO-15189 Accredited • 10,000+ patients tested • Guardant360 PMDA submission planned for 1H 2021 Asia • Guardant360 tests available in 40+ countries AMEA Middle East • 1,500+ prescribing oncologists Africa • Japan laboratory expected to be operational in 2021 30

2021 & Beyond2021 & Beyond

Guardant Health is Well Capitalized Leading into 2021 Strong year over year revenue growth ~$2B in cash and securities as of December 31, 2020 +23% +84% +23% $75M $68M $66M $61M $54M $37M Q1 19 Q1 20 Q2 19 Q2 20 Q3 19 Q3 20 32Guardant Health is Well Capitalized Leading into 2021 Strong year over year revenue growth ~$2B in cash and securities as of December 31, 2020 +23% +84% +23% $75M $68M $66M $61M $54M $37M Q1 19 Q1 20 Q2 19 Q2 20 Q3 19 Q3 20 32

Guardant Health in 2021 Transforming the continuum of cancer care Screening Recurrence Monitoring Therapy Selection • ECLIPSE registrational trial on track • Launching Guardant Reveal for use • Growing pipeline of Guardant360 for enrollment completion in 2021 in early-stage colorectal cancer CDx approvals ─ Colorectal cancer is first ─ First blood-only test with • Expanding use of Guardant360 for indication 7-day TAT tumor profiling, molecular response & longitudinal monitoring ─ More cancer types to follow─ More cancer types to follow • Launching CGP tissue assay CLINICAL DIAGNOSIS SURGERY ADJUVANT THERAPY RECURRENCE 1ST-LINE THERAPY 2ND-LINE THERAPYGuardant Health in 2021 Transforming the continuum of cancer care Screening Recurrence Monitoring Therapy Selection • ECLIPSE registrational trial on track • Launching Guardant Reveal for use • Growing pipeline of Guardant360 for enrollment completion in 2021 in early-stage colorectal cancer CDx approvals ─ Colorectal cancer is first ─ First blood-only test with • Expanding use of Guardant360 for indication 7-day TAT tumor profiling, molecular response & longitudinal monitoring ─ More cancer types to follow─ More cancer types to follow • Launching CGP tissue assay CLINICAL DIAGNOSIS SURGERY ADJUVANT THERAPY RECURRENCE 1ST-LINE THERAPY 2ND-LINE THERAPY