Objective: Mindfulness-based interventions (MBIs) are clinically effective for insomnia, but the research findings have been mixed. This meta-analysis of randomized controlled trials (RCTs) examined the effect of MBIs on insomnia. Method: Both English (PubMed, PsycINFO, Embase, and Cochrane Library databases) and Chinese (WanFang and CNKI) databases were systematically and independently searched. Standardized mean differences (SMDs) and risk ratio (RR) with their 95% confidence intervals (CIs) were calculated using the random effects model. Results: Five RCTs (n = 520) comparing MBIs (n = 279) and control (n = 241) groups were identified and analyzed. Compared to the control group, participants in the MBIs group showed significant improvement in insomnia as measured by the Pittsburgh Sleep Quality Index (n = 247; SMD: −1.01, 95% CI: −1.28 to −0.75, I = 0%, p < 0.00001) at post-MBIs assessment. Conclusion: In this comprehensive meta-analysis, MBIs appear to be effective in the treatment of insomnia. Further studies to examine the long-term effects of MBIs for insomnia are needed.