Meta-analyses indicate the efficacy of positive psychology interventions in promoting well-being. But, despite accumulating empirical and anecdotal evidence of these interventions’ implementation in real-world settings, no review of effectiveness research exists. Accordingly, we identified 40 positive psychology intervention effectiveness trials targeting adults, and scored their reporting using the practice-friendly RE-AIM tool which assesses five dimensions of intervention utility: Reach, Efficacy, Adoption, Implementation and Maintenance. Reporting levels varied substantially: reporting on Reach scored 64%; Efficacy scored 73%; Adoption scored 84%; Implementation scored 58%; and Maintenance scored 16%. Within these five dimensions, reporting on participation rates, methods to select delivery agents, differences between participants and non-participants, programme maintenance and costs, was particularly sparse. The studies involved 10,664 participants, approximately half required specialist delivery, and 12 were researcher delivered. To maximize the potential of PPIs for population health promotion, expanded reporting on effectiveness trials is required. Recommendations to assist this process are offered.