OBJECTIVE: To report a case of congenital stridor in a newborn. CASE REPORT: A newborn, delivered at term by elective cesarean, weighing 3,450 g, Apgar 9/9, was brought to the emergency room at 4-days presenting with stridor and respiratory distress noted since birth. She was tachypneic, and the inspiratory stridor was worse in the right lateral decubitus position. There were subcostal retractions. We performed a flexible fiberoptic laryngoscopy and found a large cyst in the left arytenoid obstructing the glottis during inspiration. The cyst was punctured under direct laryngoscopic observation, and the patient had immediate and complete resolution of symptoms. A second procedure was performed 30 days later due to recurrence of the symptoms. This time, we approached the cyst by complete resection of its capsule during direct laryngoscopy. The patient had a favorable outcome and remained without further respiratory symptoms as of the 6-moth follow up. CONCLUSION: Although laryngomalacia is the main differential diagnosis for congenital stridor, it is also important to evaluate endoscopically the other possible causes, including a laryngeal cyst. This is a rare condition in newborns that must be considered in infants presenting with stridor, tachypnea, and difficulty with breastfeeding. About 50% of cases are asymptomatic, but it can present as acute respiratory distress at birth. A change in head position can modify the stridor pattern, and this may be a diagnostic clue. Early stridor detection is essential, and the clinical evaluation with endoscopy is the main investigational approach. Surgical treatment is performed. Our method of endoscopic puncture followed by dissection of the cyst capsule in a second procedure proved to have a good outcome.