This study examined the association between family functioning and the development of posttraumatic stress symptoms (PTSS) in youth and parents following an unintentional traumatic injury of a child. Fifty-one parent-child dyads completed questionnaires and a structured interview assessing PTSS and family functioning. Multiple regression analyses were applied to evaluate the contribution of family functioning to the development of PTSS after controlling for demographic characteristics and known predictors. Family functioning had both direct and moderating influences on the development of PTSS in parents. We were unable to demonstrate a systematic impact of family functioning on the development of PTSS in children from the same families.