Research suggests that impaired social skills are often the most significant challenge for those with autism spectrum disorder (ASD), yet few evidence-based social skills interventions exist for adults on the spectrum. This replication trial tested the effectiveness of PEERS, a caregiver-assisted social skills program for high-functioning young adults with ASD. Using a randomized controlled design, 22 young adults 18–24 years of age were randomly assigned to a treatment (n = 12) or delayed treatment control (n = 10) group. Results revealed that the treatment group improved significantly in overall social skills, frequency of social engagement, and social skills knowledge, and significantly reduced ASD symptoms related to social responsiveness following PEERS. Most treatment gains were maintained at a 16-week follow-up assessment with new improvements observed.