Background: Few studies have examined the associations among social cohesion, physical activity, and obesity in older adults. This study explored the influences of social cohesion and leisure-time physical activity on obesity in older adults, and tested whether these relationships varied by race/ethnicity and income level. Methods: A cross-sectional analysis of adults in the 2013 National Health Interview Study (NHIS) who were over 65 years of age (N = 7714) was used. Logistic regressions were performed to examine the impacts of social cohesion and physical activity on obesity, and the relative risks (RR) were reported. Results: The median age was 73 years old, and 59.8% of respondents were female; 23.8% met the recommended level of moderate physical activity. Neighborhood social cohesion was not associated with obesity for older adults. Meeting the recommended level of vigorous physical activity was related to a lower probability of obesity only for older Hispanic adults (RR = 0.41, 95% CI: 0.31 to 0.50), while older adults were less likely to be obese if they met the recommended level of moderate physical activity. Conclusions: Increasing the level of physical activity may profoundly reduce the probability of obesity for older adults. Moreover, the results implied the need for future physical activity interventions for minorities.