Acute upper airway obstruction represents one of the most challenging emergencies in pediatric practice. In particular, a tension chylothorax complicating a malignant airway obstruction is a rare and life-threatening complication. We report a rapidly progressing tension chylothorax associated with a cervical mass in a 10-month-old male infant. To our knowledge, the extension of a cervical mass to the supraclavear region resulting in a compressive chylothorax represents an exceptional event in pediatrics. Early recognition and prompt treatment resulted to be essential to relieve the compression and to avoid end-stage hemodynamic and respiratory function derangement.