As social and built environment factors have been shown to be associated with physical activity, dietary patterns, and obesity in the general population, they likely also influence these health behaviors among cancer survivors and thereby impact survivorship outcomes. Enhancing the rich, individual-level survey and medical record data from 4,505 breast cancer survivors in the Pathways Study, a prospective cohort drawn from Kaiser Permanente Northern California, we geocoded baseline residential addresses and appended social and built environment data. With multinomial logistic models, we examined associations between neighborhood characteristics and body mass index and whether neighborhood factors explained racial/ethnic/nativity disparities in overweight/obesity. Low neighborhood socioeconomic status, high minority composition, high traffic density, high prevalence of commuting by car, and a higher number of fast food restaurants were independently associated with higher odds of overweight or obesity. The higher odds of overweight among African Americans, U.S.-born Asian Americans/Pacific Islanders, and foreign-born Hispanics and the higher odds of obesity among African Americans and U.S.-born Hispanics, compared with non-Hispanic whites, remained significant, although somewhat attenuated, when accounting for social and built environment features. Addressing aspects of neighborhood environments may help breast cancer survivors maintain a healthy body weight. Further research in this area, such as incorporating data on individuals' perceptions and use of their neighborhood environments, is needed to ultimately inform multilevel interventions that would ameliorate such disparities and improve outcomes for breast cancer survivors, regardless of their social status (e.g., race/ethnicity, socioeconomic status, nativity).