Sister Mary Joseph’s nodule is referred to as metastatic lesion of the umbilicus. Most of the tumors are adenocarcinomas originating from gastroenteric and genital tracts. Only rarely were metastases from other locations reported. We describe here an unusual case of a Sister Mary Joseph’s nodule that was metastasized from prostate carcinoma 3 years after radiation therapy. The lesion was the first sign of metastatic disease, and the diagnosis was made on skin biopsy. The patient died of extensive metastases of prostate carcinoma 4 months later. We report this case to extend the list of differential diagnosis for Sister Mary Joseph’s nodule in male patients and emphasize the importance of Sister Mary Joseph’s nodule as an ominous diagnostic sign.