Dermatomyositis is a progressive systemic disease clinically manifested by a muscle lesion with impaired motor function as well as skin rashes, often in the form of erythema. In some cases, dermatomyositis can be the onset of cancer. In this regard, the doctor is required to be highly alert and focused on detecting the tumor process in patients with progressive muscle weakness and characteristic skin manifestations of dermatomyositis. The article presents a clinical case of paraneoplastic dermatomyositis co‐existing with small cell lung cancer. The malignancy was diagnosed during cancer screening in a patient with classic manifestations of dermatomyositis. Improvement of clinical manifestations of dermatomyositis appeared with glucocorticosteroid therapy and surgical treatment, but the patient died, since small cell lung cancer has an aggressive clinical course with an unfavorable prognosis.