OBJECTIVE: This study aims to investigate the evidence of the efficacy of mindfulness-based stress reduction (MBSR) in improving stress, depression and anxiety in breast cancer patients. METHODS: An extensive systematic electronic review (PubMed, Embase, CINAHL, PsyArticles, PsycINFO, Scopus, Ovid, Web of Science and The Cochrane Library) and a hand search were carried out from 15 October 2011 to 30 November 2011 to retrieve relevant articles using 'mindfulness' or 'mindfulness-based stress reduction' and 'breast cancer' as keywords. Information about the baseline characteristics of the participants, interventions and findings on perceived stress, depression and anxiety was extracted from each study. RESULTS: Nine published studies (two randomised controlled trials, one quasi-experimental case-control study and six one-group, pre-intervention and post-intervention studies) up to November 2011 that fulfilled the inclusion criteria were analysed. The pooled effect size (95% CI) for MBSR on stress was 0.710 (0.511-0.909), on depression was 0.575 (0.429-0.722) and on anxiety was 0.733 (0.450-1.017). CONCLUSION: On the basis of these findings, MBSR shows a moderate to large positive effect size on the mental health of breast cancer patients and warrants further systematic investigation because it has a potential to make a significant improvement on mental health for women in this group.