ObjectiveTo quantify the effects of mindfulness-based therapy (MBT) on physical health, psychological health and quality of life (QOL) in patients with breast cancer. Method Studies were identified through a systematic search of six electronic databases. Randomized control trials (RCTs) examining the effects of MBT, versus a control group receiving no intervention on physical health, psychological health and QOL in breast cancer patients were included. Two authors independently assessed the methodological quality of included studies using a quality-scoring instrument developed by Jadad et al. and extracted relevant information according to a predesigned extraction form. Data was analysed using the Cochrane Collaboration’s Revman5.1. Result Finally, seven studies involving 951 patients were included. While limited in power, the results of meta-analysis indicated a positive effect of MBT in reducing anxiety [SMD −0.31, 95% CI −0.46 to −0.16, P < 0.0001], depression[SMD −1.13, 95% CI −1.85 to −0.41, P = 0.002], fear of recurrence[SMD −0.71, 95% CI −1.05 to −0.38, P < 0.0001], and fatigue[SMD −0.88, 95% CI −1.71 to −0.05, P = 0.04] associated with breast cancer, and improving emotional well-being [SMD 0.39, 95% CI 0.19–0.58, P = 0.0001], physical function[SMD 0.42, 95% CI 0.19–0.65, P = 0.0004], and physical health [SMD 0.31, 95% CI 0.08–0.54, P = 0.009] in these patients. Although the effects on stress, spirituality, pain and sleep were in the expected direction, they were not statistically significant (P > 0.05). Moreover, there is limited evidence from a narrative synthesis that MBT can improve QOL of breast cancer patients. Conclusion The present data indicate that MBT is a promising adjunctive therapy for patients with breast cancer. Due to some methodological flaws in the literature, further well-designed RCTs with large sample sizes are needed to confirm these preliminary estimates of effectiveness.