Hypertrophic pulmonary osteoarthropathy(HPO)is a tumor-associated syndrome that features the triad of clubbed fingers, periosteal bone growth in long bones, and arthritis, and is often associated with an adenocarcinoma or squamous cell carcinoma. This report presents details of a case of HPO associated with pleomorphic carcinoma, which was relieved by treatment. A 47-year-old woman was presented with a complaint of generalized arthralgia. A physical examination showed swollen joints in the body and clubbed fingers. Chest CT revealed a mass shadow in the left upper lobe and ultrasound- guided biopsy findings led to a diagnosis of non-small cell lung cancer. Furthermore, bone scintigraphy indicated symmetrical accumulation in bones and joints throughout the body. A right upper lobectomy was performed along with combined chest wall resection and mediastinal lymph node dissection with an open chest, and the presence of lung cancer complicated with HPO was indicated. Pathological examination results revealed a diagnosis of pleomorphic carcinoma(pT4N0M0, Stage ⅢA). Systemic arthralgia was resolved on the first postoperative day. One year after surgery, a solitary brain metastasis developed and was removed, with no recurrence at the time of writing. Joint symptoms related to HPO can be expected to improve with treatment of pulmonary lesions, thus aggressive procedures for diagnosis and treatment are desirable.