A 45-year-old woman with cor triatriatum sinister was admitted for laparoscopic resection of an ovarian tumor. Her medical history was benign with the exception of a single episode of syncope one year ago. A 1.5-cm membrane fenestration was found on echocardiography, but there were no other cardiac structural anomalies. General anesthesia was established with etomidate, sevoflurane, and remifentanil; no notable events occurred during the anesthesia. As cor triatriatum shows a clinical picture of mitral stenosis (MS), careful anesthetic management is required.