The authors present a new modality of endoscopic repair for unilateral choanal atresia. A 14-year old girl complained of right-sided nasal obstruction. Endoscopy and CT scans showed unilateral bony choanal atresia. The patient underwent endoscopic endonasal surgery. A mucoperiosteal flap at the posterior part of the septum in the left, healthy nasal cavity was fashioned and the denuded part of the septum was removed. The atretic choanae was resected and a unified posterior nasal opening was formed. The flap was spread over the posterior septal edge and adjusted to the opposite septal side. One-year follow-up of the patient showed no stenosis of the choanae.