While play therapy has been a recognized mode of treatment for children with social, emotional, and behavioral problems for decades, preadolescents may find the traditional playroom juvenile. Modifying the playroom and activities to specifically meet the needs of preadolescents, this study examined the effectiveness of group play/activity therapy as a school-based intervention with fourth and fifth grade learning disabled preadolescents exhibiting behavior problems. A pre-test, post-test control group design in which volunteer preadolescents were randomly assigned to either the control or treatment group was used. The group play/activity therapy intervention followed humanistic principles and was designed to address the cognitive and social-emotional needs of preadolescence. Statistical analysis revealed that preadolescents who participated in group play/activity therapy demonstrated a reduction in problem behavior. Effect size was calculated for each composite scale and subscale to determine practical significance of the treatment on the