Abstract Objective. Gestational weight gain (GWG) has been associated with overweight in offspring. The aim of the study was to assess the association of GWG with childhood overweight and a potential effect modification by maternal BMI. Methods. In a cross-sectional study of 10 784 children aged 3 to 17 years from the German national child health survey (2003-2006), main outcome measure was overweight defined by the criteria of the International Obesity Task Force. Main exposure was GWG in data-derived categories. Results. Crude and adjusted odds ratios (OR) for high and low GWG with average GWG as a reference were calculated in logistic regression models. With adjustment for potential confounders, the OR of childhood overweight for high GWG was 1.16 (95% confidence interval [CI]: 1.02, 1.32), whereas for low GWG the adjusted OR was not significant at 1.01 (95% CI: 0.89, 1.15). Stratified analyses by estimated pre-pregnancy BMI revealed inconsistent effects of high GWG on childhood overweight, with a significantly increased risk for children of normal-weight mothers only. No statistically significant advantageous effect of low GWG was present for any of the maternal BMI subgroups. Conclusion. A high compared with an average GWG accounts for a moderate increase in the risk of offspring overweight, whereas a lower than average GWG does not appear to reduce this risk. Subgroup analyses suggested that the beneficial effect of avoidance of high GWG might be confined to normal-weight mothers. Interventions promoting healthy GWG should not only target overweight and obese, but also normal-weight females.