Minimally invasive repair of pectus excavatum (MIRPE) was first reported in 1998 and has gained wide acceptance since then. A 17-year-old girl who had undergone thoracotomy and cardiac surgery for transposition of great vessels at the age of 18 months presented with a deep, long pectus excavatum with asymmetry. After initial uneventful postoperative clinical course after MIRPE, the patient had bilateral pleural and pericardial effusion on the sixth postoperative day. Suspecting postpericardiotomy syndrome, systemic steroids were administered, and the symptoms resolved without affecting wound healing. Manifestation of a pericardial effusion combined with bilateral pleural effusion after MIRPE, especially in patients after cardiac surgery, may indicate a postpericardiotomy syndrome that can be treated successfully by intravenous steroids.