Yoga has been gaining popularity as a complementary therapy for mental health conditions, but research on the efficacy of yoga is still in its beginnings. The aim of this systematic review is to investigate the effects of modern postural yoga (strong focus on physical postures) on positive mental health (PMH) indicators in clinical and nonclinical populations. The most common PMH indicators were mindfulness, affect, resilience and well-being, followed by satisfaction with life, self-compassion, empathy and others. Diverse results were found across the 14 studies analysed, including significant positive effects of yoga practice on outcome variables, to no significant effects, both in relation to baseline levels and in relation to control groups. Nonetheless, most studies observed ameliorations in PMH indicators due to yoga practice. Given that yoga interventions pose serious methodological concerns, more research and better experimental designs are needed to properly assess the effects of yoga on PMH indicators.