There is a current and growing need for evidence-based practices aimed at improving the social skills of adults with intellectual disabilities (ID). Despite an abundance of research on strategies to improve the social skills of young children with ID, there is limited research on interventions aimed at improving prosocial behaviors of adults with ID. A behavioral skills training approach was used to teach frontline, direct support professionals (DSPs) to implement a classroom management strategy called the Behavioral Opportunities for Social Skills (BOSS) program with adults with ID who lived in the community. The results showed that DSPs’ delivery of behavior-specific praise statements increased after they received training in the BOSS program. Increases in the prosocial behaviors of the adults with ID were also reported after the DSPs were trained. Social validity measures indicated that DSPs liked using the BOSS program, it was easy to implement, and the program was effective. The results of this study suggest that evidence-based social skills interventions developed for children and adolescents, including classroom management strategies, can be effective in improving prosocial behaviors of adults with ID with minimal adaptions.