The main objective of the present study was to evaluate the efficacy of peer training in pivotal response treatment (PRT) for children with autism spectrum disorder (ASD) in their first year of school. Four 6-year-old boys with ASD and eight typically developing (TD) children (aged 4-6 years) participated in the study. A non-concurrent multiple-probe (across participants) baseline design was used. Outcomes were assessed before, immediately after, and 6 to 9 weeks following an eight-session training period. Overall, rates of peer engagement increased following training for three of the four children with ASD and rates of social initiation increased following training for two of the four children with ASD; these gains were maintained at follow-up. TD peers' fidelity in implementing PRT techniques also improved. The present study suggests that relatively brief peer training in PRT can produce immediate and short-term sustained gains in peer-related social communication skills of children with ASD at school.