Dermatomyositis (DM) is a rare paraneoplastic syndrome. The case of a 47-year-old woman who was hospitalized in a neurological clinic due to non-specific neurological and dermatological symptoms is described. The results of laboratory tests (including CA 125 > 2,000 U/ml), histopathology and imaging, as well as the lack of response to treatment with steroids and methotrexate were indicative of DM in the course of malignancy. Diagnosis of primary peritoneal cancer was established on the basis of reconnaissance laparoscopy. Due to the significant weakening of muscle strength, weakening of cough reflex and swallowing disorders on the second day after surgery, the patient underwent a percutaneous tracheostomy. As a result of causative treatment with cytostatics (carboplatin with paclitaxel), paraneoplastic symptoms receded. The patient is currently in remission.