HIV incidence among young men who have sex with men (YMSM) is disproportionally high. Youth living with HIV demonstrate low rates of sustained virologic suppression (VS). Epic Allies, a theory-based behavioral intervention mobile app, utilizes self-management tools, gamification, and social support to improve engagement in care and antiretroviral adherence among YMSM living with HIV. A two-arm individually randomized-controlled trial enrolled 146 participants aged 16 to 24 years old to test the efficacy of Epic Allies to achieve VS. Both study arms showed improved VS at 26-weeks (62.9% intervention; 73.5% control; ARR = 0.93 (95% CI 0.73, 1.18)) and antiretroviral adherence; intervention effects were amplified in regular app users. Issues with recruitment and app usage metrics limit the ability to definitively say that the app was effective in causing behavior changes resulting in improved health outcomes. (ClinicalTrials.gov Identifier: NCT02782130).