Individuals with autism have difficulty with social skills across the lifespan. Few social interventions have been examined for older individuals with autism who also have significant intellectual disabilities (ID). Previous research suggests that reciprocal imitation training (RIT) improves imitation and social engagement in young children with autism. This study used a multiple-baseline design to examine whether RIT could improve social behaviors in four adolescents with autism and significant ID. All adolescents improved their spontaneous imitation and two improved their joint engagement. In addition, two adolescents decreased their rate of self-stimulatory behaviors over the course of treatment. Overall, these results suggest that RIT may be effective at improving social interaction and decreasing self-stimulatory behavior in adolescents with autism and significant ID.