Approximately 20% of children experience serious mental health problems severe enough to meet diagnosis criteria, and less than one third of these children receive the services they need. Identifying effective school-based counseling interventions provides a viable and accessible solution, especially for families with financial barriers. This randomized, controlled outcome study examined the effectiveness of Adlerian play therapy (AdPT) compared to reading mentoring (RM) with 58 kindergarten through third grade students who qualified with clinical levels of disruptive behavior in the classroom. Participants were identified as 48% Latino, 33% European American, and 19% African American. Approximately four-fifths of participants were male. Children were randomly assigned to AdPT (experimental group) or RM (active control group) for 16 sessions of treatment. Children in both groups participated in twice weekly, individual, 30-minute interventions that took place in their schools. Results from a two (group) by two (repeated measures) split plot ANOVA indicated that, compared to the RM group over time, the AdPT group demonstrated statistically significant improvement on (a) disruptive behaviors in the classroom, as directly observed by objective raters and as reported by teachers, and (b) stress in the teacher-child relationship, as reported by teachers. Teachers and observers were blinded to children's treatment group assignment. AdPT demonstrated moderate to large effect sizes on all measures, indicating the practical significance of treatment. Further, 72% of children receiving AdPT improved from clinical/borderline levels of disruptive behavior problems to more normative functioning post-intervention, demonstrating the clinical significance of results. Whereas further research is warranted, results from this preliminary study are promising and support the use of AdPT in elementary schools to meet the needs of children exhibiting disruptive classroom behavior.