IMPORTANCE: Health care was disrupted in the US during the first quarter of 2020 with the emergence of the COVID-19 pandemic. Early reports in selected samples suggested that cancer screening services decreased greatly, but population-based estimates of cancer screening prevalence during 2020 have not yet been reported. OBJECTIVE: To examine changes in breast cancer (BC), cervical cancer (CC), and colorectal cancer (CRC) screening prevalence with contemporary national, population-based Behavioral Risk Factor Surveillance System (BRFSS) data. DESIGN, SETTING, AND PARTICIPANTS: This survey study included respondents from the 2014, 2016, 2018, and 2020 BRFSS surveys who were eligible for BC (women aged 50-74 years), CC (women aged 25-64 years), and CRC (women and men aged 50-75 years) screening. Data analysis was performed from September 2021 to February 2022. EXPOSURES: Calendar year. MAIN OUTCOMES AND MEASURES: Self-reported receipt of a recent (defined as in the past year) BC, CC, and CRC screening test. Adjusted prevalence ratios (aPRs) comparing 2020 vs 2018 prevalence and 95% CIs were computed. RESULTS: In total, 479 248 individuals were included in the analyses of BC screening, 301 453 individuals were included in CC screening, and 854 210 individuals were included in CRC screening, In 2020, among respondents aged 50 to 75 years, 14 815 (11.4%) were Black, 12 081 (12.6%) were Hispanic, 156 198 (67.3%) were White, and 79 234 (29.9%) graduated from college (all percentages are weighted). After 4 years (2014-2018) of nearly steady prevalence, past-year BC screening decreased by 6% between 2018 and 2020 (from 61.6% in 2018 to 57.8% in 2020; aPR, 0.94; 95% CI, 0.92-0.96), and CC screening decreased by 11% (from 58.3% in 2018 to 51.9% in 2020; aPR, 0.89; 95% CI, 0.87-0.91). The magnitude of these decreases was greater in people with lower educational attainment and Hispanic persons. CRC screening prevalence remained steady; past-year stool testing increased by 7% (aPR, 1.07; 95% CI, 1.02-1.12), offsetting a 16% decrease in colonoscopy (aPR, 0.84; 95% CI, 0.82-0.88) between 2018 and 2020. CONCLUSIONS AND RELEVANCE: In this survey study, stool testing increased and counterbalanced a decrease in colonoscopy during 2020, and BC and CC screening modestly decreased. How these findings might be associated with outcomes is not yet known, but they will be important to monitor, especially in populations with lower socioeconomic status, who experienced greater screening decreases during the COVID-19 pandemic.