Purpose: The purpose of this study was to examine the effectiveness of a training and coaching program aimed to increase the use of the aided language modeling (ALM) strategy by siblings to support the social interactions of children with disabilities who use augmentative and alternative communication (AAC) in the natural environment. Method: A single-case multiple-probe design including a training and coaching intervention was implemented to teach 4 typically developing siblings to use the ALM strategy with high-fidelity with their sibling who used AAC. In addition, a second research question investigated the rate at which siblings used the ALM strategy with the child. Results: Results revealed that the sibling training and coaching was--(1) effective in increasing high-fidelity of the siblings' implementation of the ALM strategy; and (2) participants and family members found the intervention to be impactful and meaningful. Conclusions: The changes observed throughout this study demonstrate the need for more sibling and family-centered training to increase the use of AAC in the natural environment. Families were satisfied with the goals, procedures, and outcomes; however, they also expressed their need for additional support. [This paper was published in "American Journal of Speech-Language Pathology."]