A 53-year-old man who had a history of ulcerative colitis (UC) for 2 years underwent colonoscopy as regular follow-up. The results showed an elevated lesion in the descending colon, which was diagnosed as plasmablastic lymphoma (PBL) based on pathological findings. In situ hybridization for the Epstein-Barr virus-encoded RNA probe was positive. Fluorescence in situ hybridization revealed rearrangement of the MYC gene. He had been taking prednisolone, 5-aminosalicylic acid, azathiopurine, and ustekinumab at the diagnosis of PBL and had multiple prior therapies for UC including infliximab, tacrolimus, and tofacitinib due to steroid dependence. PBL is a rare aggressive B cell lymphoma initially described in the oral cavity of human immunodeficiency virus positive patients and it is suspected to have an association with immunocompromised status of patients. The number of cases of PBL in inflammatory bowel disease (IBD) patients is extremely rare. All these patients were administered immunosuppressive therapy including thiopurines or biologics. IBD patients with immunosuppressive therapy have a higher potential for developing lymphoproliferative disorders. Clinicians should be aware of the risk of lymphoma, including PBL.