Occupational therapists have the proven capacity to improve outcomes for young adults who are self-managing Type 1 diabetes (T1D). There is insufficient understanding of adolescents' experiences of developing responsibility for diabetes self-management (DSM). To investigate adolescents' perceptions of sharing responsibility for T1D management at school. This study had a descriptive qualitative design and used semistructured interviews and thematic analysis. It is the second phase of a mixed-methods study with a sequential explanatory design that investigated mechanisms of responsibility-sharing at school. Secondary school in Australia. Purposive sample of adolescents (age 15-16 yr) with T1D (N = 11). Adolescents approached the complex occupation of school-based DSM primarily in partnership with their parents, with each adolescent having unique responsibilities while sharing others. Health care professionals and teachers reportedly had minimal involvement. Adolescents described owning most DSM tasks, with their perceptions of building independence limiting the sharing of this responsibility. A heightened sense of risk meant that adolescents were likely to communicate with others in cases of errant blood glucose readings. Current processes commonly resulted in reduced school participation. Adolescents valued working responsively and interdependently with their parents to manage T1D at school, which aligns with the occupational therapy model of co-occupation. Effective responsibility-sharing depends on clear, frequent, autonomy-supportive, team-based communications. Our results showed that patterns of communication for determining school-based DSM processes were fragmented and risk focused, with limited adolescent involvement, resulting in strategies that led to students at times being excluded from school activities. Plain-Language Summary: This is the first study to use an occupational lens to examine the way in which adolescents share their responsibility for diabetes care at school. Diabetes self-management in secondary schools occurs more often when adolescents work interdependently with their parents to manage their diabetes. Adolescent involvement in formal school processes and a clearer allocation of team roles and responsibilities would better support health-promoting habits and school participation.