Spontaneous and asymptomatic supraclavicular thoracic duct cysts occurring in the neck are the rarest. We report a case of a huge thoracic duct cyst occurring in the supraclavicular fossa with a review of the literature and management options. A 28-year-old female had a left supraclavicular mass with a 10-year history. A cervical thoracic duct cyst was diagnosed after chemical analysis of the milky fluid obtained by preoperative fine-needle aspiration. Treatment was achieved by surgical excision of the cyst and thoracic duct ligation. Pathological analysis of the cyst after excision confirmed the diagnosis. In the case of left supraclavicular masses, the rare differential diagnosis of thoracic duct cysts must be considered as a possibility. Magnetic resonance imaging as the imaging method of choice and chemical analysis of the milky fluid obtained by preoperative fine-needle aspiration are sufficient for primary diagnosis. The treatment of this disease consists of simple excision.