Background and Aims: Single nucleotide polymorphisms in miRNA binding sites, which are located in mRNA 3' untranslated regions (3'-UTRs), were recently found to influence microRNA-target interactions. Specifically, such polymorphisms can modulatebinding affinity or create or destroy miRNA-binding sites; such variants have also been found to be associated with cancer risk. In this study, we explored the effect of a functional variant at the miR-214 binding site in the methylenetetrahydrofolate reductase gene (rs114673809) on gastric cancer (GC) risk in a hospital-based case-control study in a Chinese Han population. Methods and Results: We genotyped the rs114673809 polymorphism in 345 gastric cancer patients and 376 cancer-free controls using the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique. The functions of rs114673809 were investigated using a luciferase activity assay and validated by immunoblotting. We found that participants carrying the rs114673809 AA genotype or A allele had a significantly increased risk of gastric cancer (OR = 1.667, 95% CI = 1.044-2.660, P = 0.034; OR = 1.261, 95% CI = 1.017-1.563, P = 0.037, respectively) compared to those carrying the GG genotype and G allele. In addition, rs114673809 modified the binding of hsa-miR-214 to MTHFR as well as MTHFR protein levels in gastric cancer patients. Conclusion: Our data suggested that rs114673809, which is located at the miR-214 binding site in the 3'-UTR of MTHFR, may play an important role in the development of gastric cancer in a Chinese Han population.