This study examined the feasibility, acceptability, and preliminary efficacy of a mobile intervention called the Text-Based Adherence Game (TAG). TAG aimed to improve HIV treatment adherence among young people with HIV (YPWH) in Ghana. Participants, YPWH aged 18 to 24, were recruited from an HIV clinic in Kumasi, Ghana where study procedures were conducted. A randomized controlled pilot trial was conducted to evaluate TAG (ClinicalTrials.gov Identifier NCT03928717). Participants were randomized to receive TAG or a standard-of-care (SOC) control. All completed quantitative assessments on outcomes preintervention and at two follow-up visits at 6- and 12-months. TAG participants received personalized, semi-automated, and game-based text messages over the six-month intervention period. Primary outcomes included viral load, antiretroviral medication adherence, and missed HIV clinic visits. Secondary outcomes were also explored. Two surveys measured intervention acceptability. 60 YPWH were enrolled. 51 completed all assessments. At the 12-month follow-up assessment, TAG had a significant and positive effect on a measure of antiretroviral adherence but not viral load or missed clinic visits. Positive intervention effects were also found at postintervention and 12 months for several secondary outcomes (e.g., adherence-related social support). Intervention acceptability was generally high. TAG is a novel and promising mobile health intervention approach. Results suggest the need to further develop TAG as it may have the potential to reach populations of YPWH and improve HIV continuum of care outcomes in settings where access to more advanced mobile technology (e.g., smartphones) and the internet is not universal.