Rhabdomyomatous mesenchymal hamartoma is an extremely rare congenital lesion, and very few cases have been reported even though its macroscopic and microscopic features make diagnosis easy. An 18-year-old woman consulted with a pedunculated mass in the medial region of her neck. The mass was surgically removed, and rhabdomyomatous mesenchymal hamartoma was diagnosed. The clinical, macroscopic, histologic, and immunochemical characteristics that allow diagnosis of this entity are discussed. Although association with congenital abnormalities is uncommon, this possibility should be assessed by the clinician.