This study describes the results of an online social support intervention, called "Thrive with Me" (TWM), to improve antiretroviral therapy (ART) adherence. HIV-positive gay or bisexually-identified men self-reporting imperfect ART adherence in the past month were randomized to receive usual care (n = 57) or the eight-week TWM intervention (n = 67). Self-reported ART outcome measures (0-100 % in the past month) were collected at baseline, post-intervention, and 1-month follow-up. Follow-up assessment completion rate was 90%. Participants rated (1-7 scale) the intervention high in information and system quality and overall satisfaction (Means ≥ 5.0). The intervention showed modest effects for the overall sample. However, among current drug-using participants, the TWM (vs. Control) group reported significantly higher overall ART adherence (90.1 vs. 57.5% at follow-up; difference = 31.1, p = 0.02) and ART taken correctly with food (81.6 vs. 55.7% at follow-up; difference = 47.9, p = 0.01). The TWM intervention appeared feasible to implement, acceptable to users, and demonstrated greatest benefits for current drug users.