Carbon monoxide intoxication is an important public health problem, which may result in death. A 46-year-old male patient was found in an unconscious state at home and was transported to the emergency service by the patient's relatives. Relatives of the patients were indicated that there was gas leak from the stove. At first it was considered that the patient might be poisoned with carbon monoxide. The laboratory findings were, creatinine 2.5 mg/dL and creatinine kinase 88.15 U/L. Carboxy hemoglobin level was 30.9%. Hyperbaric oxygen therapy was commenced with the diagnosis of carbon monoxide intoxication. The laboratory values in the 2nd day of admission were, creatinine 5.8 mg/dL, creatinine kinase 88.42 U/L. Then the patient underwent a hemodialysis. Hemoglobin levels decreased to 7.3 g/dL, platelet count dropped to 11.000/mm(3). Peripheral blood smear showed erythrocyte fragmentation. Thrombotic thrombocytopenic purpura was considered and methylprednisolone and plasmapheresis was started. After the 10th session of plasmapheresis, platelet value was over 150.000/mm(3) and plasmapheresis was discontinued. Platelet value was 285.000/mm(3) and creatinine 0.7 mg/dL. The patient was discharged. Thrombotic thrombocytopenic purpura which might have complication should be kept in mind in patients with carbon monoxide intoxication.