Thymic cysts are a rare abnormality accounting for 1%-3% of all mediastinal masses. In most cases, they are asymptomatic and localized in the anterior mediastinum. Despite their benign nature, the presence of a mass is an indication for surgery to obtain a histological conclusion and reliably exclude an oncological process. Epidermoid cysts are rare and only a few cases are described in the literature. In our case report, we present a rare case of examination and treatment of a patient with a large anterior mediastinum mass, which, according to the results of histology, was an epidermoid cyst of the thymus. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.