Abstract: Objective To investigate clinical features and prognosis of breast cancer patients with type-2 diabetes mellitus in mainland China. Methods A systematic search of Cochrane library, Pubmed, EMBASE, CNKI, Wanfang and VIP from 2000 to 2014 was conducted. Case control studies combined with clinical features and prognosis of breast cancer patients with type 2 diabetes mellitus in mainland China were collected. RevMan 5.2 was used to synthesize literature data. Fixed-effect or random effects model was adopted according to heterogeneity. Results 14 studies met the inclusion criteria, including 3711 cases of patients (study group 1106 cases, 2605 cases in the control group). Diabetes was positively associated with later clinical stage (III-IV) and T stage (T3- T 4), higher recurrence rate and mortality rate 1.77 (95%CI=1.37-2.3, P<0.0001), 1.57 (95%CI=1.19-2.08, P=0.001), 1.93 (95% CI=1.56-2.39, P<0.00001), 1.64 (95%CI=1.18-2.28, P=0.03). The mean difference (mean difference, MD) for average age was 3.47 (95%CI=2.64-4.29, P=0.001) between the two groups. There were no statistical differences between other clinical features. Conclusions Our findings strongly support a relationship between diabetes and older age, later clinical stage and T stage, higher recurrence and mortality rate, and worse prognosis in breast cancer patients.