The thoracic duct cysts located in the supraclavicular region are very rare masses, the etiology of which is not completely known. This article presents the clinical follow-up of a 35-year-old male patient diagnosed with throracic duct cyst situated in the left supraclavicular region and the patient's condition is discussed in line with literature. The patient admitted to our clinic with a complaint of a mass in the left supraclavicular region that had appeared six months ago and that had been increasingly growing. A cyst excision under general anesthesia was performed to the patient who was pre-diagnosed with thoracic duct cyst following the radiological evaluation and the needle aspiration biopsy. There were no complications or a recurrence during the six months of postoperative follow-up.