ABSTRACT.To evaluate long-term outcomes for siblings of children with traumatic brain injury (TBI), measures of sibling relationships and sibling behavior were collected an average of 4 years postinjury. The study sample included participants in a larger longitudinal study who had school-aged siblings, including 34 with severe TBI, 30 with moderate TBI, and 39 with orthopedic injuries not involving brain insult (ORTHO group). Group comparisons revealed more negative sibling relationships in families of children with TBI than in families of children in the ORTHO group, but only for mixed-gender sibling pairings. Behavior problems in children with TBI predicted both sibling relationships and sibling behavior problems. The findings indicate a need to monitor the adjustment of siblings and sibling relationships after TBI and to include siblings in family interventions.