BACKGROUND: Phone-delivered counseling has demonstrated improved health outcomes for people living with HIV. However, counseling is hampered by a lack of guidance on the frequency and duration of intervention in relation to clinical benefits. The added benefits of bidirectional (ie, interactive) vs. unidirectional (ie, passive) text messages to augment counseling are also unknown. We conducted a clinical trial of adaptive phone counseling along with either bidirectional or unidirectional text messaging for people living with HIV. METHODS: A community sample of 425 young people (aged 16-36 years) living with HIV in Georgia, USA, received weekly phone counseling sessions with the number of sessions determined by the participant and their counselor. Participants were subsequently randomized to either (1) weekly bidirectional text messages with their counselor or (2) weekly automated unidirectional text message reminders. Participants were followed for 16 months to assess 3 primary outcomes: antiretroviral therapy (ART) adherence, HIV care engagement, and HIV suppression. RESULTS: Participants demonstrated improved clinical outcomes over the follow-up period, with 74% of those who were not taking ART initiating treatment, 65% of those on ART improving adherence, and 47% who had detectable viral loads at baseline attaining viral suppression. The number of sessions completed predicted improved ART adherence, greater care engagement, and HIV suppression over follow-ups. Bidirectional text messages impacted care engagement by moderating the effects of counseling sessions on HIV suppression. CONCLUSIONS: Phone counseling augmented by bidirectional text messages has the potential to improve HIV care for young adults living with HIV.