Summary Inflammatory bowel disease consists of multifactorial diseases whose common manifestation is inflammation of the gastrointestinal tract and their pathogenesis remains unknown. This study aimed to analyse the gene polymorphisms in Brazilian patients with inflammatory bowel disease. A total of 101 patients diagnosed with inflammatory bowel disease were analysed for the tumour necrosis factor‐alpha (‐308 G/A; rs1800629) and interleukin‐10 (‐1082 G/A; rs1800896) gene polymorphisms. Genotyping was performed through polymerase chain reaction–sequence‐specific primer, then fractionated on 2% agarose gel and visualized after staining by ethidium bromide. The anatomic–clinical form of Crohn's disease (CD) predominant was the inflammatory (32.75%), followed by fistulizing (29.31%) and 27.58% stricturing. As control group, a total of 136 healthy subjects, from the same geographical region, were enrolled. The statistical analyses were performed using R program. The frequency of the A allele at tumour necrosis factor‐alpha was high in ulcerative colitis (UC) patients (51%) than in controls (22%; P > 0.01). No statistical difference was found with the genotypic and allelic frequencies of CD patients compared to controls (P = 0.54). The polymorphism ‐1082G/A of interleukin‐10 was not statistical different between the diseases compared to controls. Tumour necrosis factor‐alpha (TNF‐α) (‐308G/A) is associated with UC onset, suggesting that the presence of ‐308A allele could confer a relative risk of 3.62 more to develop UC in general population. Further studies, increasing the number of individuals, should be performed to ratify the role of TNF‐α in the inflammatory bowel disease pathogenesis.