Religiosity has been associated with greater body weight. Less is known about South Asian religions and associations with weight. Cross-sectional analysis of the MASALA study (n = 906). We examined associations between religious affiliation and overweight/obesity after controlling for age, sex, years lived in the USA, marital status, education, insurance status, health status, and smoking. We determined whether traditional cultural beliefs, physical activity, and dietary pattern mediated this association. The mean BMI was 26 kg/m2. Religious affiliation was associated with overweight/obesity for Hindus (OR 2.12; 95 % CI: 1.16, 3.89), Sikhs (OR 4.23; 95 % CI: 1.72, 10.38), and Muslims (OR 2.79; 95 % CI: 1.14, 6.80) compared with no religious affiliation. Traditional cultural beliefs (7 %), dietary pattern (1 %), and physical activity (1 %) mediated 9 % of the relationship. Interventions designed to promote healthy lifestyle changes to reduce the burden of overweight/obesity among South Asians need to be culturally and religiously tailored.