There are more than a million persons living with HIV in the United States. Despite the effectiveness of antiretroviral therapy (ART), viral suppression, particularly durable viral suppression, can be difficult to achieve. Suboptimal ART adherence plays a significant role in unsuccessful viral suppression, which increases the risk of disease progression, a shortened lifespan, transmission to others, and the development of treatment resistant strains of HIV. As a result, interventions targeting adherence have been developed. There have been some signs of success, particularly with more intensive interventions. However, there is a need to develop efficacious ART adherence interventions that are readily disseminable and make efficient use of available resources. To that end, PI Ramsey developed and tested an mHealth facilitated ART adherence intervention that includes a single face-to-face ART adherence session delivered by a health coach, followed by 12 months of access to an app and health coaching delivered via the app. The app generates a push notification medication reminder, and adherence data are available to the health coach via a "dashboard," allowing the health coach to monitor adherence in real time and provide support. The health coach uses a two-way secure messaging feature on the app to message participants and to provide support, encouragement, and resources, including links and attachments, in response to adherence lapses and in response to participant-generated messages. The combination of a face-to-face intervention component followed by app facilitated health coaching represents a novel combination that affords participants with a personal connection to a health coach while minimizing the resources needed to deliver the intervention and maximizing timely responsiveness to adherence lapses and other participant needs. A preliminary randomized controlled trial (RCT) compared the intervention to a control condition in which participants received the single face-to-face ART adherence session alone. Based on pilot data, the protocol and intervention are highly feasible and acceptable, and results are consistent with preliminary efficacy of the intervention on objective measures of ART adherence. This study will expand on this preliminary test of the intervention using a fully powered RCT (n=400) across two sites (Providence, RI and Atlanta, GA). The long-term goal of this line of research is to disseminate an efficacious, mHealth facilitated ART adherence intervention that can be readily integrated into clinical care. This study will examine the impact of the intervention, relative to control, on electronic pillbox ART adherence and viral load data. In addition, the role of theoretically supported variables in the mediation and moderation of intervention effects will be explored. Interviews will be conducted at baseline, 1, 3, 6, and 12 months. A subset of participants will also complete interviews at 18 and 24 months to explore sustained intervention effects. If found efficacious, the intervention could be broadly integrated into clinical care for HIV, reducing morbidity and mortality among PLWH in a manner that makes efficient use of available resources.