Abstract Background: Obesity is associated with risk of aggressive prostate cancer. It is not known whether neighborhood obesogenic factors are independently associated with prostate cancer risk. Methods: Neighborhood socioeconomic status (nSES) and four neighborhood obesogenic environment factors (urbanicity, mixed-land development, unhealthy food environment, and parks) were assessed for associations with prostate cancer risk among 41,563 African American, Japanese American, Latino, and White males in the Multiethnic Cohort (MEC) Study, California site. Multivariable Cox proportional hazards regression was used to estimate HRs and 95% confidence intervals (CI) for nonaggressive and aggressive prostate cancer, adjusting for individual-level sociodemographic, behavioral, and prostate cancer risk factors. Analyses were stratified by race, ethnicity, and, among Latino males, nativity. Results: Males residing in low-SES, compared with high-SES, neighborhoods had lower risk of nonaggressive prostate cancer [lowest vs. highest quintile HR = 0.81; 95% confidence interval (CI) = 0.68–0.95, Ptrend 0.024], driven by a similar trend among foreign-born Latino males. Foreign-born Latino males in neighborhoods with low mixed-land development had increased risk of non-aggressive disease (lowest vs. highest quintile HR = 1.49; 95% CI = 1.07–2.09). For aggressive disease, the only association noted was between lower mixed-land development and lower risk among White males (Ptrend = 0.040). Conclusions: nSES and obesogenic environment factors were independently associated with prostate cancer risk; associations varied by race, ethnicity, nativity, and disease aggressiveness. Impact: Upstream structural and social determinants of health that contribute to neighborhood obesogenic characteristics likely impact prostate cancer risk differently across groups defined by race, ethnicity, and nativity and by disease aggressiveness.