Primary carcinosarcoma of the prostate is an extremely rare and aggressive malignancy. We report a patient who presented with obstructive symptoms and without a history of radiation, prior adenocarcinoma, or androgen deprivation therapy. Transurethral resection of the prostate was performed. Histopathology and immunohistochemistry revealed a confirmatory diagnosis of de novo carcinosarcoma of the prostate. The case is described for its rarity and masquerading nature.