HIV-infected youth experience many stressors, including stress related to their illness, which can negatively impact their mental and physical health. Therefore, there is a significant need to identify potentially effective interventions to improve stress management, coping, and self-regulation. The object of the study was to assess the effect of a mindfulness-based stress reduction (MBSR) program compared to an active control group on psychological symptoms and HIV disease management in youth utilizing a randomized controlled trial. Seventy-two HIV-infected adolescents, ages 14-22 (mean age 18.71 years), were enrolled from two urban clinics and randomized to MBSR or an active control. Data were collected on mindfulness, stress, self-regulation, psychological symptoms, medication adherence, and cognitive flexibility at baseline, post-program, and 3-month follow-up. CD4+ T lymphocyte and HIV viral load (HIV VL) counts were also pulled from medical records. HIV-infected youth in the MBSR group reported higher levels of mindfulness (P = .03), problem-solving coping (P = .03), and life satisfaction (P = .047), and lower aggression (P = .002) than those in the control group at the 3-month follow-up. At post-program, MBSR participants had higher cognitive accuracy when faced with negative emotion stimuli (P = .02). Also, those in the MBSR study arm were more likely to have or maintain reductions in HIV VL at 3-month follow-up than those in the control group (P = .04). In our sample, MBSR instruction proved beneficial for important psychological and HIV-disease outcomes, even when compared with an active control condition. Lower HIV VL levels suggest improved HIV disease control, possibly due to higher levels of HIV medication adherence, which is of great significance in both HIV treatment and prevention. Additional research is needed to explore further the role of MBSR for improving the psychological and physical health of HIV-positive youth.