Although most children recover quickly after a mild traumatic brain injury (TBI), a sizeable minority suffer negative long-term consequences. Thus, the objective of this study was to investigate functional outcomes in children after mild TBI and to examine post-acute post-concussive symptoms (PCS) and neurocognitive test performance as predictors. Children, ages 8 to 16, were recruited (135 with mild TBI and 70 with orthopedic injury). Participants and their parents provided ratings of functioning at baseline, 3 and 6 months post-injury. Although groups differed in functioning shortly after injury, no differences were apparent at 3 or 6 months. Post-acute PCS were significant predictors of parent- and child-reported functioning at 3 and 6 months. Neurocognitive test performance predicted child-reported functioning (but not parent-reported) when considered independently, but did not add incrementally to prediction above PCS. The findings suggest that higher levels of PCS put children at risk for poor functioning after an injury.