This study compared immediate and 4-month outcomes among adolescents with autism spectrum disorder randomly assigned to the PEERS curriculum (n = 10), a peer mediated PEERS curriculum (n = 12), or a delayed treatment control group (n = 12). Findings suggest a modest advantage in social skills knowledge and social functioning for participants in the peer-mediated PEERS curriculum relative to Traditional PEERS, and gains in social skills knowledge, social functioning, and reductions in loneliness were maintained in one or both treatment groups at a 4-month follow-up. Typically developing peer mentors (n = 16) showed improvements in social skills knowledge and marginal improvements in autism knowledge and loneliness. Future research with a larger sample and objective outcome measures is needed.