BACKGROUND: Ileum adenocarcinoma (IA), a type of small bowel adenocarcinoma, is a rather uncommon factor associated with obstruction in small bowel. Owing to its location and indefinite clinical symptoms, the diagnosis of IA is difficult, and survival is usually poor. With respect to the rarity of this disease, very few studies have reported such cases to provide a reference for treatment. CASE SUMMARY: In this manuscript, a case of a 48-year-old man presented with chronic right lower abdominal pain and distention, queasiness and emesis. A computed tomography scan revealed intestinal wall thickening and an intestinal obstruction in the terminal ileum. He was diagnosed with inflammatory bowel disease. However, his symptoms were not relieved after conservative treatment. The patient subsequently underwent exploratory laparotomy, and a tumour in the ileum measuring approximately 2.0 cm × 2.0 cm that was located 20 cm from the ileocolic valve was discovered incidentally and was operatively resected along with the enlarged lymph nodes. Pathological examination revealed a stage IIA (T3N0M0) ulcerative IA. Along with imaging examinations, a diagnosis of primary IA with no lymph or distant metastases was considered. The patient was discharged and recovered well as of the writing of this manuscript. CONCLUSION: IA should be considered as a differential diagnosis in cases of intestinal obstruction, and the recommended method for local disease treatment is surgery.