Interleukin (IL) 17A is an inflammatory cytokine expressed by Th 17 cells and plays a role in tissue inflammation by inducing release of proinflammatory and neutrophil-mobilizing cytokines. We have investigated the association between colorectal cancer and polymorphisms of IL17A (rs2275913. G197A). The study was performed in 241 subjects (102 with colorectal cancer and 139 healthy controls). Genotypes were determined by fluorescent-based restriction fragment length polymorphism method. The association between the molecular features at the gene in relation to tumor and patient clinical characteristics was analyzed. There was a significant difference between the genotype frequencies of IL17A G197A of control subjects (GG 68.34 % and GA + AA 31.65 %) and patients with colorectal cancer (GG 47.05 % and GA + AA 52.94 %) (p = 0.001 with odds ratio (OR) 2.45 (1.43-4.11)). IL17A G197A polymorphism is particularly associated with colon cancer. Indeed, the IL17A GG genotype could be considered as a protective factor against colon cancer (p = 0.00001) with OR 3.77 (2.04-6.99). We have noted a significant association of IL17A G197A polymorphism not only with tumor localization (p = 0.003) but also with tumor differentiation (p = 0.0005) in CRC patients. We have also showed a significant association of G197A variant with an increased risk of advanced stage (p = 0.005). Our result suggests that the A allele of IL17A gene is involved in susceptibility to colorectal cancer and is associated with clinical features as tumor location, tumor differentiation, and TNM stage. IL17A polymorphism may serve as biomarker of disease location and progression.