A 69-year-old female patient was referred to our hospital, following the working diagnosis of an ovarian tumor detected during a physical examination of her lower back, owing to pain. Chest computed tomography revealed a tumor affecting the left lung, as well as multiple liver, bone, and lymph node metastases. Moreover, the left ovarian tumor was confirmed on imaging. After initiation of radiotherapy for the bone metastases, a biopsy of the left ovarian tumor was performed. Histopathological analysis revealed a small cell carcinoma, and immunostaining was positive for thyroid transcription factor-1. A secondary ovarian malignancy from the small cell lung carcinoma was diagnosed based on the imaging and histopathological findings. A secondary ovarian malignancy from a small cell lung carcinoma is clinically difficult to differentiate from a primary ovarian carcinoma; a comprehensive judgment based on imaging and pathological findings is necessary.