Desmoid tumor is one kind of fibromatosis, and much occurs the abdominal wall and outside the abdominal wall. Intra- abdominal desmoid tumor is rare at about 8%. We experienced a case of intra-abdominal desmoid tumors occurring 4 years after open radical prostatectomy with some literature review. A 72-year-old man had undergone open radical prostatectomy for prostate cancer. Four years after that resection, multiple intra-abdominal tumors measuring 56 mm in maximum diameter was identified on follow-up computed tomography, and he was referred to our department for management. We performed laparotomy and investigation of the biopsy. Immunohistochemistry of the resected specimen indicated the tumor cells were positive for vimentin and β-catenin, and the diagnosis was desmoid. We performed partial resection of the small intestine and ileocecal resection. His postoperative course was uneventful and he was discharged on the 12th postoperative day. He has shown no sign of recurrence in the 4 months follow-up since surgery. In the past, an operation was the best treatment for intra-abdominal desmoid tumor. But it is reported that watchful waiting is also possible by the case which has no symptom and dysfunction in NCCN guidelines 2019. Further research is needed.