Cervical thymic cyst is rare lesions leading to cervical mass. As it is a rare entity, it might be confused with other congenital neck masses or neoplastic lesions. Preoperative diagnosis is almost impossible. In the present study, a patient who was operated with prediagnosis of branchial cyst and diagnosed with thymic cyst according to the histopathologic examination was presented. A 16-month-old girl was admitted to our clinic with the complaint of growing right neck mass that was realized about 4 months ago. Magnetic resonance imaging (MRI) of the neck demonstrated a rim-enhanced hypointense cystic lesion in the posterior aspect of the submandibular gland, without tracheal right lateral and mid plane on MRI, curving common carotid artery to the medial. Patients underwent surgery under general anesthesia in company with existing findings. Hypoglossal nerve was surrounded by the mass, and the mass was totally resected. The final pathology result was reported as thymic cyst. Cervical thymic masses might be unnoticed in the differential diagnosis of the cervical mass as they are rarely seen entities. Histopathologic examination of the thymus tissue was performed for diagnosis. Surgical excision is the ideal treatment approach and no postoperative recurrence has been reported.