To examine associations between walkability, metropolitan size, and physical activity (PA) among cancer survivors and explore if the association between walkability and PA would vary across United States metropolitan sizes. This study used data fromthe 2020 National Health Interview Surveyto examine independent associations of walkability and metropolitan size with engaging in moderate-to-vigorous PA (MVPA) and toexplore the effect modification of metropolitan sizeusing log-binomial regression. The dependent variable was dichotomized as < vs. ≥ 150min/week of MVPA. The predictors were perceived walkability, a total score comprising eight neighborhood attributes, and metropolitan size. Covariates included sociodemographic and health characteristics, geographic region, cancer type, and time since cancer diagnosis. Engaging in 150 + min/wk of MVPA significantlyincreased among cancer survivors (n = 3,405) who perceived their neighborhoods as more walkable (prevalence ratio:1.04; p = 0.004). Engaging in 150 + min/wk of MVPA significantlyincreased among cancer survivors living in mediumand small metropolitan areas vs. those living in largecentral metropolitan areas (prevalence ratio:1.12; p = 0.044). Perceived walkability levels were similar among cancer survivors in nonmetropolitan areas vs. those living in largecentral metropolitan areas. Association between walkability and PA did not significantly vary across metropolitan sizes. Perceived neighborhood walkability is positively associated with MVPA among cancer survivors, regardless of metropolitan size. Findings highlight the importance of investing in the built environment to increase walkability among this population and translating lessons from mediumand small metropolitan areas to other metropolitan areas to address the rural-urban disparity in PA among cancer survivors.