Epidermoid cysts (EC) are the most common tumors of the skin. They are usually asymptomatic and small-sized. They are more common at young ages. They grow slowly and are painless. The wall of EC is covered with epidermis-like epithelium. EC are rarely seen in sinuses. In our case, a 16-year-old female presented with complaints of swelling and headache that started from the left eye and extended to the upper lip. A biopsy was performed at another hospital of the patient who had previously received medical treatment but had no complaints. A cystic mass containing teeth was observed in the left maxillary sinus on imaging. The cystic mass was excised along withthe wall. Pathological results supported the diagnosis of EC. Treatment of EC are surgical and recurrence rates are low. Although many masses are observed in the sinonasal region, epidermoid cysts are rare. It is important to distinguish epidermoid cysts from malignant masses that exhibit expansile growth characteristics. Keywords: Headache, epidermoid cyst, maxillary sinus