Objective We reviewed studies published from 1990 to 2010 examining the relation of peer influence to diabetes outcomes for adolescents with type 1 diabetes. Methods We searched PsychInfo and MedLine databases and personal archives for studies meeting our criteria. 24 articles were included in the final review. Results Qualitative studies revealed that teens believe peers have an impact on diabetes behaviors, but quantitative findings are inconclusive. We found more evidence that social conflict was harmful than social support was helpful. Associations were more likely in studies that measured specific support and specific self-care variables. Studies addressing how individual differences interact with social context had promising findings. Conclusions The literature linking peer relations to diabetes outcomes is mixed. Future research should consider moderator variables, expand the conceptualization of peer relationships, and consider interactions between person and social context.