This case presents a technique for doing family therapy in families with young children. In family play therapy, the entire family plays together, allowing full participation of even the youngest children in the therapeutic process. Standard family therapy interventions in the latter part of each session make use of family interaction patterns and unconscious processes revealed during the earlier play. In the case presented here, the technique was successfully applied to a family with a 3-year-old son who had functional urinary retention. This case also provided an opportunity for interdisciplinary collaboration between the separate Child and Family Services at a major teaching hospital.