Lung cancer metastases to the prostate are uncommon, and are usually found incidentally during autopsy. This case report describes a 77-year-old man with a large cell neuroendocrine carcinoma (LCNEC) of the lung and metastases from this primary cancer in the prostate. During the follow-up after the chemotherapy performed for pulmonary LCNEC, pelvic computed tomography revealed a prostatic tumor and prostatic needle biopsy was performed. Histologically, the tumor was identified as LCNEC, forming a tissue architecture closely resembling the previously diagnosed lung cancer. The tumor cells were immunohistochemically positive for thyroid transcription factor-1. These findings led to a diagnosis of prostatic metastasis of pulmonary LCNEC.