Peer relationships play a crucial role in promoting the development and well-being of all youth, including children and adolescents with intellectual disabilities. This chapter provides a review of the literature on peer relationships among youth with intellectual disabilities. The chapter is structured into four main sections that: (a) frame intellectual disability through a social-ecological lens; (b) review empirical research on peer acceptance, bullying, social interactions and participation, and friendships; (c) present a multidimensional approach to assessment that includes individual and environmental factors impacting peer relationships; and (d) describe key principles and evidence-based interventions to promote peer interaction and relationships for youth with intellectual disabilities. Two key conclusions emerged from the review of this research. First, the quality of peer relationships varies widely among youth with intellectual disabilities, but many need support to experience positive interactions and friendships. Individual and environmental factors, such as communication skills, behavior, support needs, and participation opportunities, are associated with peer acceptance. Second, environmental factors, especially support for meaningful inclusion in shared activities with peers, facilitate the formation of meaningful friendships. This chapter emphasizes the need for collaborative, inclusive practices to promote genuine, reciprocal peer relationships among youth with intellectual disabilities in school and community settings.