The aim of this study was to examine, through the roles of peers with regards to diabetes, the relationship between the support perceived by adolescents with diabetes and their peer-group affiliation. This is a descriptive, phenomenological and retrospective study based on a qualitative methodology. In-depth interviews with 15 people aged 18–35 with type 1 diabetes mellitus diagnosed in their childhood or adolescence were carried out. Data was analyzed through the interpretation of general discourses. Peers have considerable influence on adolescents and provide them social support from different roles. The protective role basically offers emotional support and sends reminders of different aspects of the treatment, while the indifferent role does not meddle in any aspect related to the diabetes. Both roles can foster social integration of adolescents with diabetes into the peer group. The offender role creates social conflicts through discrimination and stigma of adolescents with diabetes. These roles appear during the process of socialization of adolescents with diabetes, where commensality and situations of self-monitoring or administering insulin, key aspect of diabetes treatment, are crucial. Peer groups, depending on the role adopted, may offer support or bring a specific conflict regarding diabetes to their adolescent peer. The combination of roles that friends and peer group play with regards to diabetes will determine the degree of socialization and integration of adolescents with diabetes.