Adolescents living with HIV (ALHIV) face many psychosocial challenges, including HIV disclosure to others. Given the importance of socialization during the adolescent transition process, this study investigated the psychological and social factors influencing self-disclosure of own HIV status to peers. We examined social HIV self-disclosure to peers, and its relationship to perceived HIV-related stigma, self-efficacy to disclose, self-esteem, and social support among a sample of n = 582 ALHIV aged 13-17 years in Kampala, Uganda, and Western Kenya. Data were collected between February and April 2011. Among them, 39% were double orphans. We conducted a secondary data analysis to assess the degree of social disclosure, reactions received, and influencing factors. Interviewer-administered questionnaires assessed medical, socio-demographic, and psychological variables (Rosenberg self-esteem scale; self-efficacy to disclose to peers), HIV-related stigma (10-item stigma scale), and social support (family-life and friends). Descriptive, bivariate, and logistic regression analyses were performed with social self-disclosure to peers with gender as covariates. Almost half of ALHIV had told nobody (except health-care providers) about their HIV status, and about 18% had disclosed to either one of their friends, schoolmates, or a boy- or girlfriend. Logistic regression models revealed that having disclosed to peers was significantly related to being older, being a paternal orphan, contributing to family income, regular visits to the HIV clinic, and greater social support through peers. Low self-efficacy to disclose was negatively associated to the outcome variable. While social self-disclosure was linked to individual factors such as self-efficacy, factors relating to the social context and adolescents' access to psychosocial resources play an important role. ALHIV need safe environments to practice disclosure skills. Interventions should enable them to make optimal use of available psychosocial resources even under constraining conditions such as disruptive family structures.