Parents and peers have been successful at implementing interventions targeting social interactions in children with autism; however, few interventions have trained siblings as treatment providers. This study used a multiple-baseline design across six sibling dyads (four children with autism) to evaluate the efficacy of sibling-implemented reciprocal imitation training. All six typically developing siblings were able to learn and use contingent imitation, four of the six siblings were able to learn and use linguistic mapping, and all six siblings increased their use of at least one component of the imitation training procedure. Three of the four children with autism showed increases in overall imitation and all four showed evidence of increases in joint engagement. Parents and siblings reported high satisfaction with the intervention, and ratings by naïve observers indicated significant changes from pre- to posttreatment. These results suggest that sibling-implemented reciprocal imitation training may be a promising intervention for young children with autism.