Objective To explore the therapeutic effects of trimetazidine (TMZ) on diabetic patients with coronary heart diseases.Methods We conducted a comprehensive electronic search of PubMed, EMBASE, and Cochrane databases between the inception dates of databases and May 2019 (last search conducted on 30 May 2019) to identify randomized controlled trials. The evaluation method recommended by Cochrane Collaboration for bias risk assessment was employed for quality assessment. Random or fixed models were used to investigate pooled mean differences in left ventricular function, serum glucose metabolism, serum lipid profile, myocardial ischemia episodes and exercise tolerance with effect size indicated by the 95% confidence interval (CI).Results Additional TMZ treatment contributed to considerable improvement of left ventricular ejection fraction (WMD=4.39, 95%CI: 3.83, 4.95, P<0.00001), left ventricular end diastolic diameter (WMD=-3.17, 95%CI: -4.90, -1.44, P=0.0003) and left ventricular end systolic diameter (WMD=-4.69, 95%CI: -8.66, -0.72, P=0.02). TMZ administration also significantly decreased fasting blood glucose (SMD=-0.43, 95%CI: -0.70, -0.17, P=0.001), glycosylated hemoglobin level (WMD=-0.59, 95%CI: -0.95, -0.24, P=0.001), serum level of total cholesterol (WMD=-20.36, 95%CI: -39.80, -0.92, P=0.04), low-density lipoprotein cholesterol (WMD=-20.12, 95%CI: -32.95, -7.30, P=0.002) and incidence of myocardial ischemia episodes (SMD=-0.84, 95%CI: -1.50, -0.18, P=0.01). However, there were no significant differences in serum triglyceride level, high-density lipoprotein cholesterol, exercise tolerance between the TMZ group and the control group. Conclusion TMZ treatment in diabetic patients with coronary heart disease is effective to improve cardiac function, serum glucose and lipid metabolism and clinical symptoms.