An 81-year-old woman lost consciousness and was taken to our hospital 3 days after colonoscopy was performed as a follow-up of endoscopic mucosal resection done 1 year ago for early sigmoid colon cancer detection. She had left hypochondrial pain. Based on abdominal contrast-enhanced computed tomography (CT) findings, she was diagnosed with abdominal bleeding due to injury to the lower splenic pole, and an urgent splenectomy was performed. In this case, there was no abdominal trauma to cause splenic injury. Injury to the lower splenic pole during colonoscopy was considered due to the adhesion found in the abdominal cavity. It is possible that the hemorrhage did not stop because she was taking antiplatelet drugs.