There is little agreement within the literature regarding the relationship between executive function and social outcome following paediatric traumatic brain injury (TBI). It has been suggested that the inconsistent findings may be due to the lack of a proposed mechanism through which this relationship exists. Yeates and colleagues (2004) propose a possible model in which the maturity of social problem solving skills mediates the relationship between executive function and social outcome. This study explored the relationship between executive function and social outcome, and whether social problem solving mediated this relationship. The long-term outcome of executive functioning and social functioning following the transition into adulthood, and their relationship with injury severity was also examined. The sample consisted of 36 adolescents and young adults who sustained a closed head injury between 8-13 years of age. Adolescents and young adults who suffered moderate/severe TBI during childhood displayed executive dysfunction and poorer social outcomes, with the maturity of social problem solving skills mediating the relationship between executive function and social outcome.