Solitary rectal ulcer syndrome (SRUS) is an uncommon benign disease that is misdiagnosed as malignancy or inflammatory bowel disease because of similarities in clinical and endoscopic manifestations. Furthermore, SRUS with ulcerative colitis (UC) is extremely rare. To date, two cases have been reported in the medical literature. We report an additional case of SRUS with UC that was misdiagnosed as rectal cancer. A 61-year-old man was admitted to our hospital with rectal bleeding. Colonoscopy showed a well-demarcated, shallow, ulcerative lesion with polypoidal growth involving the entire circumference of the rectal lumen. Findings from imaging studies, including abdominal computed tomography (CT) and positron emission tomography (PET)/CT resembled those of rectal cancer. Surgical resection was performed because clinical symptoms persisted despite medical treatment and because occult rectal cancer could not be ruled out. Histopathological examination of the resected specimen revealed fibromuscular obliteration of the lamina propria and crypt abscesses, characteristics compatible with SRUS and UC.