SummaryObjectiveIndependent of weight status, rapid weight gain has been associated with underlying brain structure variation in regions associated with food intake and impulsivity among pre‐adolescents. Yet, we lack clarity on how developmental maturation coincides with rapid weight gain and weight stability.MethodsWe identified brain predictors of 2‐year rapid weight gain and its longitudinal effects on brain structure and impulsivity in the Adolescent Brain Cognitive Development^SM Study®. Youth were categorized as Healthy Weight/Weight Stable (WS_HW, n = 527) or Weight Gainers (WG, n = 221, >38lbs); 63% of the WG group were healthy weight at 9‐to‐10‐years‐old.ResultsA fivefold cross‐validated logistic elastic‐net regression revealed that rapid weight gain was associated with structural variation amongst 39 brain features at 9‐to‐10‐years‐old in regions involved with executive functioning, appetitive control and reward sensitivity. Two years later, WG youth showed differences in change over time in several of these regions and performed worse on measures of impulsivity.ConclusionsThese findings suggest that brain structure in pre‐adolescence may predispose some to rapid weight gain and that weight gain itself may alter maturational brain change in regions important for food intake and impulsivity. Behavioural interventions that target inhibitory control may improve trajectories of brain maturation and facilitate healthier behaviours.