BACKGROUND Traumatic subserosa hematoma of the proximal jejunum with delayed rupture and hemorrhage is exceedingly rare, especially without anticoagulation. No prior reports document spontaneous rupture precisely on day 5 post-blunt trauma. This case uniquely demonstrates this delayed pattern, initial computed tomography (CT) misdiagnosis as a retroperitoneal neoplasm due to Treitz ligament proximity, and conservative management failure, offering novel insights into its unpredictable course and