Malignant hyperthermia (MH) is a rare but one of the most serious complications of general anesthesia due to the hypermetabolic state of skeletal muscle. In this case, it was aimed to share the diagnosis and treatment of the patient who was diagnosed with MH intraoperatively during cardiac surgery. Consent was obtained from the 59-year-old patient who was scheduled for CABGx2 surgery on his beating heart. The patient had no comorbidities other than hypertension. He was a non-smoker and had no history of previous surgery. Hypermetabolic findings began in the 90th minute of the operation. Body temperature: 39°C; pCO2: 72 mmHg; pH: 7.15; potassium was 5.13 mEq/L and pulse was >120.min-1. MH was considered when the color change in soda lime started. After these findings, anesthesia was maintained with 100% oxygen and TIVA anesthesia. The patient, whose hemodynamic stabilization was achieved, was taken to the intensive care unit (ICU) in an intubated state at the end of the surgery. A single dose of 2.5 mg/kg iv dantrolene was administered in the ICU. After dantrolene, body temperature, hemodynamic and metabolic values returned to normal. The patient was extubated on the first postoperative day. The patient, who was followed up in the ICU for 2 days and in the ward for 5 days, was discharged without complications. Dantrolene is the specific antidote for MH. With early application, the risk of complications and mortality can be reduced. Therefore, attention should be paid to the clinical symptoms of MH, and as soon as MH is suspected, triggering agents should be removed immediately and dantrolene supply and treatment should be provided.