A three-year-old girl was admitted to Hacettepe Children's Hospital due to sweating and poor feeding. Echocardiography demonstrated ostium primum atrial septal defect with a cleft mitral valve. After two months of medical follow-up with digitalis, she was subjected to open-heart surgery, and a primum-type atrial septal defect with double mitral orifice was found. To avoid creating acute mitral stenosis, the cleft was only partially sutured and the septal defect was closed with a patch. Her postoperative recovery was uneventful. It is emphasized that surgical intervention should be individualized in each case.