Thymectomy, the surgical removal of the thymic gland, is essential in cases of thymoma. The majority of cases of a myasthenia gravis (MG) represent a relative indication for thymectomy which requires cooperation with specialized neurologists. Patients with MG may present with a tumor of the thymic gland. In case of suspicious thymoma, the resectability of the tumor has to be evaluated in the preoperative diagnostic. The clinical condition of patients with MG has to be stabilized preoperatively. The aim of thymectomy is the radical removal of thymoma and/or maximal improvement of MG symptoms. This requires the complete extirpation of the thymic gland including all ectopic thymic tissue in the anterior mediastinum. There is a variety of surgical techniques for performing a complete thymectomy. In addition to the conventional techniques with sternotomy, the significance of minimally-invasive approaches is increasing rapidly. Despite the ongoing scarcity of data of higher evidence concerning the procedure of thymectomy an increasing number of equivalent results with minimally-invasive operation techniques for MG and for thymoma are available. The successful surgical performance of a thymectomy is part of an interdisciplinary cooperation in the perioperative treatment of MG as well as the postoperative long-term care for patients with MG and/or thymoma.