Thymic cysts are uncommon tumors which usually occur in the neck and mediastinum. It is known to arise from embryonic remnants of the thymopharyngeal duct or from infammation of thymic tissues. Patients with thymic cyst are often asymptomatic and identified after surgical removal and histologic examination. We experienced a 73 year-old man with recently developed dyspnea. During the examination, chest CT showed a $5{ imes}6cm$ sized cystic mass causing deviation of the trachea. It was located in between the right thyroid gland and anterior mediastinum. It also caused tracheal narrowing noted by bronchoscopy. Right anterior cervical incision and removal of the mass was performed and a histological diagnosis of thymic cyst was confirmed. The patient was discharged without complication.