The DNA methyltransferase 3A (DNMT3A) -448A>G polymorphism is a novel functional single nucleotide polymorphism (SNP) that contributes to the genetic susceptibility to gastric cancer. In this study, we aimed to assess the genotype frequencies of DNMT3A -448A>G in colorectal cancer (CRC) patients and healthy control subjects, and to explore the association of the DNMT3A functional SNP, -448A>G, with genetic susceptibility to CRC. Genomic DNA was extracted from samples of 258 patients with CRC and 280 healthy controls. Polymerase chain reaction-restriction fragment length polymorphism analysis was employed to assess the genotype frequencies of DNMT3A -448A>G in all of the subjects. Stratification analyses were used to study subgroups of subjects by age and gender, and to evaluate the association between the DNMT3A -448A>G polymorphism and the genetic susceptibility to CRC. The allele frequency of -448A among CRC patients and the controls was 26.4 versus 19.8%, respectively. Overall, we found that compared with GG carriers, the DNMT3A -448AA homozygotes had a 3.692-fold increased risk of CRC. Stratification analysis showed a significant difference in this SNP between the CRC patients and the control subjects of different genders. AA homozygotes carried an increased risk in the subgroup of individuals aged ≥50 years in male CRC. Compared with GG homozygotes in females aged ≥50 years, the AG and AA genotypes carried a 0.355-fold decreased risk in this subgroup. These data imply that the DNMT3A SNP -448A>G contributes to genetic susceptibility to CRC. -448A>G may be used as a stratification marker to predict the susceptibility of certain individuals to CRC, particularly in male individuals aged ≥50 years.