OBJECTIVE: To examine the association between self-reported leisure-time moderate- to vigorous-intensity physical activity (MVPA) and obesity among non-Hispanic White, non-Hispanic Black, Hispanic, and Asian Americans. METHODS: We analyzed data from 569,816 Whites, 54,521 Blacks, 44,864 Hispanics, and 11,232 Asians aged 18 to 79 years who participated in the 2007 and 2009 Behavioral Risk Factor Surveillance System. Physical activity, height, weight, and demographic data were self-reported through telephone interviews. MVPA level was categorized into inactive, low, medium, and high, and weight status into normal-weight, overweight, and obese based on body mass index. Race/ethnicity-, sex-, and age group-specific polytomous logistic regression analysis was conducted, adjusted for age, education, and income. RESULTS: There was an inverse association between self-reported MVPA and obesity among White men and women (Ps for trend <.0001). Black and Hispanic women also presented an inverse association (Ps for trend <.0001), although the association was weaker compared to White women. In Asians, no association between self-reported MVPA and obesity was observed. CONCLUSIONS: Weak or no association observed between self-reported MVPA and obesity in minority groups may: 1) suggest that other factors than MVPA play more critical roles in determining weight status in minority groups, or 2) reflect large measurement errors of self-report data in minority groups.