BACKGROUND: Ethnic minorities/immigrants have differential health as compared with natives. The epidemic in child overweight/obesity (OW/OB) in Sweden is leveling off, but lower socioeconomic groups and immigrants/ethnic minorities may not have benefited equally from this trend. We investigated whether nonethnic Swedish children are at increased risk for being OW/OB and whether these associations are mediated by parental socioeconomic position (SEP) and/or early-life factors such as birth weight, maternal smoking, BMI, and breastfeeding. METHODS: Data on 10,628 singleton children (51% boys, mean age: 4.8 y, born during the period 2000-2004) residing in Uppsala were analyzed. OW/OB was computed using the International Obesity Task Force's sex- and age-specific cutoffs. The mother's nativity was used as proxy for ethnicity. Logistic regression was used to analyze ethnicity-OW/OB associations. RESULTS: Children of North African, Iranian, South American, and Turkish ethnicity had increased odds for being overweight/obese as compared with children of Swedish ethnicity (adjusted odds ratio (OR): 2.60 (95% confidence interval (CI): 1.57-4.27), 1.67 (1.03-2.72), 3.00 (1.86-4.80), and 2.90 (1.73-4.88), respectively). Finnish children had decreased odds for being overweight/obese (adjusted OR: 0.53 (0.32-0.90)). CONCLUSION: Ethnic differences in a child's risk for OW/OB exist in Sweden that cannot be explained by SEP or maternal or birth factors. As OW/OB often tracks into adulthood, more effective public health policies that intervene at an early age are needed.