The objective was to assess the nature, rate, predictive factors, and neurocognitive correlates of novel psychiatric disorders (NPD) after mild traumatic brain injury (MTBI). Children age 5-14 years with MTBI (N=87) from consecutive admissions to five trauma centers were enrolled and studied with semistructured psychiatric interviews soon after injury (baseline), and 70 of these children were assessed again 6 months post-injury. Injury severity; lesion characteristics; pre-injury variables, including psychiatric disorder, family psychiatric history, family functioning, socioeconomic status, psychosocial adversity, and adaptive functioning; and post-injury neurocognitive and adaptive functioning measures were assessed with standardized instruments. NPD occurred in 25 of 70 participants (36%) in the first 6 months after injury. NPD at 6 months was predicted by the presence of frontal white-matter lesions on MRI at 3 months post-injury, and was associated with concurrent decrements on neurocognitive indices of processing speed, expressive language, and intellectual functioning. NPD was not predicted by other indices of severity, pre-injury psychosocial variables, estimated pre-injury academic functioning, or adaptive and executive function decrements 6 months post-injury. These findings suggest that short-term psychiatric morbidity associated with MTBI in children and adolescents may be more common than previously thought and may have readily identifiable neuroimaging and neurocognitive correlates.