Cell cycle checkpoint kinase 2 (CHEK2) is a checkpoint kinase that plays an important role in the DNA damage signaling network. Numerous epidemiological studies have evaluated the association between the CHEK2 I157T variant and cancer susceptibility. However, the results of these studies on the association remain conflicting. The main purpose of this study was to integrate previous results and explore whether the CHEK2 I157T variant is associated with cancer susceptibility. PubMed, Embase (before 2012-10-1), Google Scholar, and CBMdisc were searched for studies on the relationship of the CHEK2 I157T variant and the incidence of cancer. Eligible articles were included for data extraction. The main outcome was the frequency of CHEK2 I157T polymorphisms between cases and controls. Comparison of the distribution of SNP was mainly performed using Review Manager 5.0. The odds ratio (OR) and its 95% confidence interval (95% CI) were used to assess the strength of association. In total, 26,336 cases and 44,219 controls from 18 case-control studies were used in this meta-analysis, and significant associations of the CHEK2 I157T variant with cancer susceptibility were found (OR, 1.39; 95% CI, 1.19-1.63; p<0.0001), breast cancer (OR=1.58, 95% CI=1.42-1.75, p<0.00001) and colorectal cancer (OR=1.67, 95% CI=1.24-2.26, p=0.0008). We also found an association of the CHEK2 I157T variant with familial cases (OR=1.85, 95% CI=1.51-2.26, p<0.00001). However, the association was not established for other types of cancer (OR=1.09, 95% CI=0.75-1.57, p=0.66). This meta-analysis demonstrates that the CHEK2 I157T variant was an important cancer gene, which increases cancer risk, especially in breast and colorectal cancer in Caucasian, and the bioinformatic analysis showed this change was mainly attributed to the decreased hydrophobicity of CHEK2 157T.