AIDS-related mortality among HIV-positive adolescents has risen by 50% despite the scale up of antiretroviral therapy (ART). ART maladherence likely plays a role in the increase of AIDS-related deaths among adolescents and has shown to be associated with psychosocial and mental health difficulties. Addressing the specific mental health needs of HIV-positive adolescents is critical to ending the HIV epidemic. This cross-sectional study prospectively enrolled HIV-positive adolescents (12-24 years) in Moshi, Tanzania. A structured questionnaire was administered that included questions about home, school, adherence, and measures of stigma (Berger Stigma Scale) and mental health. Mental health measures included depression (Patient Health Questionnaire-9), emotional/behavioral difficulties (Strengths and Difficulties Questionnaire), and traumatic experiences/post-traumatic stress symptoms (The University of California Los Angeles-post-traumatic stress disorder-Reaction Index). Mental health difficulties were prevalent among HIV-positive adolescents and were associated with incomplete adherence and stigma. Resources are needed to reduce HIV stigma and address mental health among HIV-positive adolescents in low-resource settings. This will improve not only mental health, but may also improve ART adherence and virologic suppression, improving overall health of the individual and reducing the risk of HIV transmission to others.