OBJECTIVE: Mindfulness-based stress reduction (MBSR) is a potentially effective supplement for the treatment of insomnia; however, there is no comprehensive review of its mental health effects among insomnia patients. This study aimed to synthesize relevant quantitative evidence and evaluate MBSR application and effectiveness for insomnia patients' sleep quality and mental health. METHODS: A systematic search through eight databases from the earliest available dates until August 2019 was conducted. Randomized controlled trials assessing the effects of MBSR on sleep quality, anxiety, and depression as outcome measures among insomnia patients comprising patients aged above 18 years were included in this meta-analysis. Each study's quality was assessed using the modified Jadad quality scale. The Review Manager 5.3 software was used to calculate the standardized mean differences (SMD) with 95% confidence intervals (CIs) for the data analyses. RESULTS: In total, data for 497 patients in seven randomized controlled trials were analyzed. The results revealed that compared to the control group, the MBSR group significantly improved in sleep quality (SMD = -0.69, 95% CI: -1.12~ - 0.26, Z = 3.16, p = .002), depression (SMD = -1.83, 95% CI: -2.81-0.84, Z = 3.63, p < .001), and anxiety (SMD = -1.74, 95% CI: -2.90-0.59, Z = 2.96, p = .003). A sensitivity analysis was undertaken. After carefully reviewing included trials, we can reasonably conclude that these heterogeneities did not impair the overall effect size of MBSR in the results. CONCLUSIONS: MBSR significantly improved sleep quality and mental health. Future research is needed using standardized methods examining the long-term effects of MBSR on the mental health of individuals with insomnia.