Background: Both obesity and developmental disabilities have increased in recent decades. Limited studies suggest associations between maternal prepregnancy obesity and child neurodevelopment. Methods: The Infant Feeding Practices Study II, a US nationally distributed longitudinal study of maternal health and infant health and feeding practices, was conducted from 2005 to 2007. In 2012, mothers were recontacted for information on their children’s health and development. We examined associations between maternal prepregnancy BMI and child psychosocial development in 1311 mother-child pairs included in this follow-up study. Children’s development was assessed by maternal report of child psychosocial difficulties from the Strengths and Difficulties Questionnaire, past developmental diagnoses, and receipt of special needs services. Results: Adjusting for sociodemographic factors, children of obese class II/III mothers (BMI >35.0) had increased odds of emotional symptoms (adjusted odds ratio [aOR] 2.24; 95% confidence interval [CI], 1.27-3.98), peer problems (aOR 2.07; 95% CI, 1.26-3.40), total psychosocial difficulties (aOR 2.17; 95% CI, 1.24-3.77), attention-deficit/hyperactivity disorder diagnosis (aOR 4.55; 95% CI, 1.80-11.46), autism or developmental delay diagnosis (aOR 3.13; 95% CI, 1.10-8.94), receipt of speech language therapy (aOR 1.93; 95% CI, 1.18-3.15), receipt of psychological services (aOR 2.27; 95% CI, 1.09-4.73), and receipt of any special needs service (aOR 1.99; 95% CI, 1.33-2.97) compared with children of normal weight mothers (BMI 18.5-24.9). Adjustment for potential causal pathway factors including pregnancy weight gain, gestational diabetes, breastfeeding duration, postpartum depression, and child’s birth weight did not substantially affect most estimates. Conclusions: Children whose mothers were severely obese before pregnancy had increased risk for adverse developmental outcomes.