This systematic review and meta-analysis comprehensively evaluates the effectiveness of mobile health (mHealth) interventions on antiretroviral therapy (ART) adherence among HIV-positive adults. Through rigorous analysis of 38 randomized controlled trials involving 12,847 participants across 25 countries, we demonstrate that mHealth interventions significantly improve medication adherence, viral suppression, and retention in care. The most substantial benefits were observed with two-way text messaging systems that incorporated personalized feedback and medication reminders. Subgroup analyses revealed particularly strong effects among key populations including young adults, pregnant women, and individuals with documented adherence challenges. These findings provide robust evidence to guide the implementation and scale-up of mHealth strategies in diverse HIV care settings.