OBJECTIVE: The impact that congenital heart disease (CHD) has on the neurodevelopment of children with Down syndrome (DS) is unknown and potentially has implications for targeted early intervention. This study assessed the relationship between CHD that required surgery in the first year of life and neurodevelopmental, behavioral and emotional functioning outcomes in children with DS. METHODS: A retrospective chart review of 1092 children (0-18 years) with DS who visited a single institution from 8/08-8/13 was performed. Children who underwent at least one of nine neurodevelopmental (cognitive, language, developmental) or academic tests were included in the analysis (N = 178). Cohort was age-divided into infants/toddlers (0-2 years), preschoolers (3-5 years), and school age/adolescent (6-18 years). Test scores of children with DS who underwent cardiac surgery in the first year of life were compared to children with DS without CHD. T test, chi-square and Mann Whitney U tests were used where appropriate. RESULTS: Infants/toddlers with cardiac surgery had lower scores for receptive (P = .01), expressive (P = .021) and composite language (P < .001) compared to those with no CHD. Preschoolers with cardiac surgery had lower language scores and lower visual motor scores, although not statistically significant. In school age children with cardiac surgery there were no differences in IQ scores, language scores, or academic achievement scores compared to those without CHD. Also at school-age there was no difference in the incidence of ADHD, executive function or on internalizing and externalizing behavior scores. CONCLUSION: Children with DS undergoing cardiac surgery during the first year demonstrated poorer neurodevelopmental outcomes as infants/toddler but had no difference at school age compared to children with DS without CHD. These results will guide early interventions to optimize neurodevelopmental outcomes in children with DS and will help with family counseling after CHD repair.