Adolescents living with HIV require engagement with care providers in order to access the critical medical and psychosocial services they need. The current study sought to explore developmental determinants of adherence to medical appointments as one aspect of engagement in care among a geographically diverse sample of 200 gay/bisexual male adolescents (16-24 years) living with HIV, with a specific focus on ethnic identity, sexual orientation identity, and identity as a young man living with HIV. Ethnic identity affirmation (OR = 0.6; 95% CI: 0.3, 0.9), morality of homosexuality (OR = 1.7; 95% CI: 1.2, 2.5), and HIV-positive identity salience (OR = 1.5; 95% CI: 0.9, 2.4) were associated with significantly higher risk for missed appointments in the past 3 months. These findings highlight the importance of attending to developmental factors, such as the development of multiple identities, when attempting to increase engagement in care for gay/bisexual male adolescents living with HIV.