||The current study evaluated the effectiveness of the Superhero Social Skills program in increasing the social engagement skills and decreasing the aggressive behavior of students with externalizing behavior problems as implemented by a resource teacher. There have been no empirical evaluations of the Superhero Social Skills program as implemented by educators other than graduate students in school psychology familiar with the program. The Superhero Social Skills program was administered to 5 elementary age participants with training occurring for 30 minutes twice per week in a public elementary school. The participating resource teacher taught 11 lessons from the program across 11 weeks. Effects were primarily assessed through a momentary time sampling procedure during both analog (structured free play) and recess (unstructured play) situations, for intervention and follow-up phases. The momentary time sampling recorded each participant's percentage of time spent socially engaged (initiating and responding) and/or engaged in aggression (verbal and physical). Both effect sizes and the percentage of all nonoverlapping data points (PAND) were calculated. Pre- and posttreatment effects were also evaluated for the Social Skills Improvement System (SSIS) and the Behavior Assessment System for Children, 2nd Edition (BASC-2). Consumer satisfaction, social validity, and treatment integrity factors were also examined. Results indicated that the Superhero Social Skills program had a small effect in enhancing participants' social engagement with peers and had a medium effect in reducing aggressive behavior of student participants. Positive social engagement was observed to generalize from the instructional setting to the natural setting of recess. The current study also found that the Superhero Social Skills program was implemented with a high rate of fidelity (85%) by a resource teacher unfamiliar with the program as measured by treatment integrity probes across each lesson. Additionally, the participating resource teacher rated the program as easy to implement and the Superhero Social Skills program was rated as being socially valid, acceptable, and effective by the student participants, parents, and teachers.