Cor-triatriatum sinister (CTS) is a rare congenital condition in which the left atrium is divided into two chambers. Patients can present as infants or later in life, which is largely dependent on the size of fenestration between these two chambers. Surgical excision of the membrane is curative. This is traditionally performed through a median sternotomy. Here we report of a case of a 60-year old man who presented to his primary care physician with dyspnea and atrial fibrillation. He was found to have CTS. We performed excision of the left atrial membrane and maze procedure through a left anterolateral mini-thoracotomy with femoral cannulation.