Intramural gastrointestinal hematomas are commonly observed following abdominal trauma or are associated with coagulopathy disorders. In contrast, idiopathic gastrointestinal hematoma is rare, and colonic involvement is sporadic, with very few published reports. We report the case of a 29-year-old female who presented with right hypogastric pain over the last three days. Abdominal CT with contrast revealed an 8.5 × 6 × 7.5 cm pre-occlusive intramural hematoma of the ascending colon up to the hepatic flexure with diffuse edematous wall thickening, indicating colonic obstruction. On colonoscopy, the site of the intramural hematoma was identified without active bleeding or obvious pathology, and the colonoscope successfully passed through the region. The patient was managed conservatively. A month later, abdominal CT revealed complete resolution of the colonic hematoma. After two months of follow-up, the patient was free from gastrointestinal symptoms. In conclusion, idiopathic colon intramural hematoma is rare, with a challenge in diagnosis and treatment; efforts should be made to treat it with conservative therapy.