Objective: This prospective longitudinal study investigated sleep disturbance (SD) and internalizing problems after traumatic injury, including traumatic brain injury (TBI) or extracranial/bodily injury (EI) in children and adolescents, relative to typically developing (TD) children. We also examined longitudinal relations between SD and internalizing problems postinjury. Method: Participants (N = 87) ages 8–15 included youth with TBI, EI, and TD children. Injury groups were recruited from a Level 1 trauma center after sustaining vehicle-related injuries. Parent-reported SD and internalizing problems were assessed at preinjury/baseline, and 6 and 12 months postinjury. Linear mixed models evaluated the relation of group and time of assessment on outcomes. Results: Controlling for age, the combined traumatic injury group experienced significantly higher postinjury levels of SD (p = .042) and internalizing problems (p = .024) than TD children; however, TBI and EI injury groups did not differ from each other. Injury severity was positively associated with SD in the EI group only, but in both groups SD was associated with additional postinjury sequelae, including fatigue and externalizing behavior problems. Internalizing problems predicted subsequent development of SD but not vice versa. The relation between injury and SD 1 year later was consistent with mediation by internalizing problems at 6 months postinjury. Conclusions: Children with both types of traumatic injury demonstrated higher SD and internalizing problems than healthy children. Internalizing problems occurring either prior to or following pediatric injury may be a risk factor for posttraumatic SD. Consequently, internalizing problems may be a promising target of intervention to improve both SD and related adjustment concerns.