In recent years, with the rising incidence of patients having long-term Crohn's disease, there has been an increase in the number of reports of carcinogenesis from dysplasia with chronic inflammation as the primary pathogenic factor. We hereby report a case of multiple metastases that appeared 5 years after surgery, in a patient with rectal cancer who had Crohn's disease. A man in his 50s was diagnosed with Crohn's disease which affected his small and large intestines 21 years back. The patient was being treated with oral steroids, 5-aminosalicylic acid, and modified nutrition. Infliximab was added to the treatment after it was introduced 11 years ago. He also had a history of rectal cancer and had undergone surgery for the same 5 years back. He was diagnosed with stage II cancer, and had not received any adjuvant chemotherapy. However, 5 years after surgery, multiple metastases recurred, and chemotherapy with mFOLFOX6 was administered. Additionally, for treating his Crohn's disease, which was also active, infliximab was changed to vedolizumab;however, the patient died a year later. Colorectal cancer accompanied with Crohn's disease has a higher risk of developing metastasis and is associated with poorer prognosis as compared to the noncomplicated colorectal cancer. Regarding treatment modalities, while searching for multidisciplinary treatment methods centered on surgical treatment in collaboration with medical oncologists and radiologists, the safety of treatment for Crohn's disease in patients with cancer must be borne in mind. The rising prevalence of cases of colorectal cancer with Crohn's disease is expected to lead to the formulation of specialized diagnostic and treatment strategies for these patients.