BACKGROUND Choanal atresia with a supernumerary nostril located on the columella is extremely rare. Infants are obligate nasal breathers because the oral airway is invariably blocked during calm respiration. Infants breathe through the mouth only during crying, and they only have nasal breathing until 5 months of life. Congenital nasal anomalies have been reported to be fatal from birth, requiring tracheal intubation or tracheostomy in the early postnatal period. In these cases, it is crucial to maintain an adequate airway. CASE REPORT A 2948-g female infant was born at 40 weeks by normal vaginal delivery. Her Apgar scores were 9 and 9 at 1 and 5 min, respectively. She had retractive breathing, cyanosis, and a supernumerary nostril at birth. She had no other anomalies. Computed tomography showed bilateral membranous choanal atresia. She needed nasal continuous positive pressure or a high-flow nasal canula for oxygen desaturation during crying, apnea, and dyspnea. However, her respiratory symptoms did not improve completely. On day 25 of life, she was given a mouthpiece to support mouth breathing. Her respiratory symptoms improved gradually, and she was discharged on day 73 of life with a mouthpiece. CONCLUSIONS A very rare case of choanal atresia with a supernumerary nostril located on the columella was described. A mouthpiece was effective for breathing, obviating the need for emergency surgical intervention in the early postnatal period. Emergency procedures were avoided, probably because this case involved incomplete bilateral membranous choanal atresia rather than complete bony atresia.