Our goal was to prospectively study the course of oppositional defiant disorder (ODD) symptomatology in children and adolescents in the first 2 years after traumatic brain injury (TBI). Fifty children aged 6 to 14, hospitalized after TBI, were assessed soon after TBI regarding injury severity; preinjury psychiatric, socioeconomic, family functioning, and family psychiatric history status; and neuroimaging was analyzed. ODD symptomatology in the first year after TBI was related to preinjury family function, social class, and preinjury ODD symptomatology. Increased severity of TBI predicted ODD symptomatology 2 years after injury. Change (from before TBI) in ODD symptomatology at 6, 12, and 24 months after TBI was influenced by socioeconomic status. Only at 2 years after injury was severity of injury a predictor of change in ODD symptomatology. The influence of psychosocial factors appears greater than severity of injury in accounting for ODD symptomatology and change in such symptomatology in the first but not the second year after TBI in children and adolescents. This appears related to persistence of new ODD symptomatology after more serious TBI.