Background: Pulmonary actinomycosis may create a diagnostic and therapeutic dilemma especially in cancer patients. Case Report: A 64-year-old male patient presented with a productive cough, bloody sputum, and weight loss. Thoracic computed tomography (CT) showed a 5-cm mass in the upper lobe of the right lung, and a 2-cm mass in the lower lobe of the left lung. Bronchoscopic examination did not show any endobronchial lesions. CT-guided needle biopsy of the right pulmonary lesion showed lung adenocarcinoma. Whole-body positron emission tomography/CT revealed an increase in fluorodeoxyglucose accumulation in the upper lobe of the right lung, in the lower lobe of the left lung, and in the right hilar and paratracheal lymph nodes. Before chemotherapy was initiated, the patient had to be admitted to the hospital because of massive hemoptysis. Bronchoscopic examination indicated persistent bleeding in the left lower lobe bronchus. The patient underwent diagnostic left thoracotomy, and wedge resection of the lower lobe mass. The diagnosis was pulmonary actinomycosis, and the patient received oral amoxicillin. He underwent successful surgery for the primary disease following 6 cycles of chemotherapy. Conclusion: Oncologists should be aware of rare diseases that may affect management approaches in the treatment of cancer.