Background Insomnia is a widespread and debilitating condition that affects sleep quality and daily productivity. Although mindfulness meditation (MM) has been suggested as a potentially effective supplement to medical treatment for insomnia, no comprehensively quantitative research has been conducted in this field. Therefore, we performed a meta-analysis on the findings of related randomized controlled trials (RCTs) to evaluate the effects of MM on insomnia. Methods Related publications in PubMed, EMBASE, the Cochrane Library and PsycINFO were searched up to July 2015. To calculate the standardized mean differences (SMDs) and 95% confidence intervals (CIs), we used a fixed effect model when heterogeneity was negligible and a random effect model when heterogeneity was significant. Results A total of 330 participants in 6 RCTs that met the selection criteria were included in this meta-analysis. Analysis of overall effect revealed that MM significantly improved total wake time and sleep quality, but had no significant effects on sleep onset latency, total sleep time, wake after sleep onset, sleep efficiency, total wake time, ISI, PSQI and DBAS. Subgroup analyses showed that although there were no significant differences between MM and control groups in terms of total sleep time. Significant ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT effects were found in total wake time, sleep onset latency, sleep quality, sleep efficiency, and PSQI global score (absolute value of SMD range: 0.44–1.09, all p < 0.05). Conclusions The results suggest that MM may mildly improve some sleep parameters in patients with insomnia. MM can serve as an auxiliary treatment to medication for sleep complaints.