Introduction: Colonoscopy is routinely performed test in the diagnosis and prevention of colon diseases. Splenic rupture is a rare complication, 80 cases described so far. Case study: Patient at age 72, hospitalized with anaemia. During the colonoscopy – polypectomy of sigmoid colon polyp. In the second day after treatment: the morning syncope, hypotension, positive peritoneal signs. Additional examinations: X‑ray: no change, USG and CT scan: splenic rupture with a large hematoma, a large amount of blood in the peritoneal cavity. The patient was qualified for laparotomy by which it was found: blood in the peritoneal cavity, spleen rupture, liver capsule ruptured, stomach with a small hematoma, mesentery colon hematoma, no perforation of the colon. Discussion: Splenic rupture is a rare but serious complication of colonoscopy. Mechanisms leading to splenic rupture: direct trauma, traction system ligament, pulling adhesions between the spleen and the purse. Start of symptoms could occur as from 1 hour up to 2.5 days, usually until 24 hours after colonoscopy. Time to determine the diagnosis: as from 2 hours up to 13 days, mostly before 24‑48 hours. The most commonly used methods for the diagnosis: CT scan, USG. Conclusion: Persons performing endoscopic examination as well as patients undergoing colonoscopy should be aware of the possibility of splenic rupture. In the case of indication of the factors predisposing to complications, in asymptomatic patients an observation for 24 hours after the colonoscopy is recommended as well as USG. If symptoms of splenic rupture appeared, USG and CT should be urgently carried out.