Introduction: Depression in emerging adults (20-29 years of age), a transition from adolescence to adulthood, is a mental health problem globally. Antidepressants and psychotherapy have limited effectiveness and might not be available worldwide. Alternative and complementary treatments, such as mindfulness meditation, are growing. Objective: We examined the effects of mindfulness interventions on depression in emerging adults and explored the moderating effects of participants, methods, and intervention characteristics. Design: Systematic review and meta-analysis. Subjects: Emerging adults. Interventions: Mindfulness meditation interventions versus control groups. Outcomes measures: depressive symptoms. Results: Forty-five studies resulted in 49 comparisons, including 3479 participants (23.0-2.7 years old); 1826 participants practiced mindfulness and 1653 served as controls. Overall, mindfulness interventions showed significant reduction in depression compared with controls (g = 0.44, 95% confidence interval: 0.33-0.55). Mindfulness interventions conducted in Asian countries had a greater decrease in depression (g = 0.69) than studies conducted in North America (g = 0.44) or Europe (g = 0.23). Mindfulness interventions showed greater reductions in depression in studies with higher proportion of females (Slope = 0.010, τ(2) = 0.07, Q(between) = 7.10, p = 0.008). Mindfulness interventions conducted in emerging adults with depressive disorders reduced depression more (g = 1.12) than in emerging adults without (g = 0.40). Providing mindfulness intervention in a group setting had a greater reduction of depression (g = 0.54) than on an individual basis (g = 0.30). More minutes of unstructured mindfulness practice per session showed a greater reduction in depressive symptoms (Slope = 0.016, Q(between) = 1.34, p = 0.035). Using intention-to-treat analyses showed a lower ES (g = 0.14) than not using it (g = 0.55). Other quality indicators were not significant moderators. Primary researchers did not report the adverse effects of mindfulness interventions. Conclusion: Mindfulness interventions somewhat improved depression in emerging adults. Because primary researchers did not report the adverse effects, mindfulness interventions should be used with caution. Future researchers might study the adverse effects of mindfulness interventions as well as the long-term effects.