Objective. This article aims to assess the effects of ginger (Zingiber officinale Roscoe) on type 2 diabetes mellitus (T2DM) and/or components of the metabolic syndrome (MetS). Methods. Electronic literature was searched in PubMed, Embase, the Cochrane Library, Chinese Biomedical Database, China National Knowledge Infrastructure, and Wanfang Database from inception of the database to May 19, 2017, and supplemented by browsing reference lists of potentially eligible articles. Randomized controlled trials on research subjects were included. Data were extracted as a mean difference (MD) and 95% confidence interval (CI). Subgroup analysis of fasting blood glucose (FBG) was performed. Results. 10 studies met the inclusion criteria with a total of 490 individuals. Ginger showed a significant beneficial effect in glucose control and insulin sensitivity. The pooled weighted MD of glycosylated hemoglobin (HbA1c) was −1.00, (95% CI: −1.56, −0.44; P<0.001). Subgroup analysis revealed that ginger obviously reduced FBG in T2DM patients (−21.24; 95% CI: −33.21, −9.26; P<0.001). Meanwhile, the significant effects of improvement of lipid profile were observed. Most analyses were not statistically heterogeneous. Conclusion. Based on the negligible side effects and obvious ameliorative effects on glucose control, insulin sensitivity, and lipid profile, ginger may be a promising adjuvant therapy for T2DM and MetS.