The red wine polyphenol, resveratrol, is highly effective in treating type 2 diabetes mellitus (T2DM) in animal models, but there is no consensus regarding its efficacy in humans. We conducted a systematic review, which included searches in nine scholarly databases and six clinical trial registries, and identified randomized controlled clinical trials whereby resveratrol was used as an adjunct to pharmaceutical interventions in T2DM. Meta-analysis on clinical parameters was performed for available data. Of 764 articles originally identified, data from six unique datasets, examining a total of 196 T2DM patients (104 resveratrol, 92 control/placebo) ultimately met inclusion criteria. Statistically significant (p < 0.05) positive effects, indicating that resveratrol supplementation was more effective than placebo/control, were identified for systolic blood pressure, hemoglobin A1c, and creatinine, but not for fasting glucose, homeostatic model assessment of insulin resistance, diastolic blood pressure, insulin, triglycerides, LDL, or HDL cholesterol. No major adverse events were reported and side effects of resveratrol were not different than placebo/control. Though limitations in sample size and treatment duration preclude definitive changes in clinical practice, significant improvements in multiple cardiometabolic biomarkers and an excellent safety profile support resveratrol as a leading candidate as an adjunct to pharmacological management of T2DM.