BackgroundTo investigate the long-term outcome of pediatric mild traumatic brain injury (mTBI) in terms of neurocognitive, behavioral, and school functioning and to identify clinical risk factors for adverse outcomes. MethodsThis study describes the follow-up of a prospective multicenter sample of 89 children with mTBI 3.6 years postinjury and 89 neurologically healthy children matched for sex, age, and socioeconomic status. Neurodevelopmental outcomes were assessed using an intelligence test, behavioral questionnaires, computerized neurocognitive tests, and longitudinal (pre- and postinjury) standardized school performance data. ResultsChildren with mTBI exhibited intelligence in the average range but had more behavioral problems related to inattentiveness (P = 0.004, d = 0.47) and hyperactive impulsivity (P = 0.01, d = 0.40) and showed poorer neurocognitive performance in information processing stability (P = 0.003, d = −0.55) and Visual Working Memory (P = 0.04, d = −0.39) compared with matched peers. Longitudinal school performance data revealed poorer performance in Technical Reading up to two years postinjury (P = 0.005, d = −0.42) when compared with normative data. Clinical risk factors did not reveal predictive value for adverse outcomes in children with mTBI. ConclusionsThis study indicates that children with mTBI are at risk of long-term deficits in neurocognitive and behavioral functioning, with longitudinal evidence suggesting shortfalls in school performance up to two years postinjury. Clinical risk factors do not provide a solid basis for long-term neurodevelopmental prognosis. Findings emphasize the importance of, and challenges for, early identification of children at risk for adverse neurodevelopmental outcome after mTBI.