Pooled results presented that MTHFR C677T polymorphism was significantly associated with type 2 diabetes mellitus (T2DM) under homozygous (odds ratio [OR] = 1.61, 95% confidence interval [CI] = 1.37–1.90), heterozygous (OR = 1.32, 95% CI = 1.15–1.51), recessive (OR = 1.39, 95% CI = 1.22–1.58), dominant (OR = 1.40, 95% CI = 1.22–1.60), and allele (OR = 1.32, 95% CI = 1.20–1.45) genetic models. The gene discussed is MTHFR; the disease is type 2 diabetes mellitus.