Primary liposarcoma of the spermatic cord (LSC) is a rare neoplasm; there are fewer than 100 cases reported in the English literature worldwide. A seventy-one year-old man, who had undergone radical retropubic prostatectomy (RRP) for localized prostate cancer in November 2004, noticed the enlargement of a mass in the left scrotum. Subsequently he underwent a biopsy of the lesion, which documented suspicion of leiomyosarcoma of the spermatic cord. Left radical orchiectomy was performed extending to the resection margin. The pathological examination showed a dedifferentiated liposarcoma of the left spermatic cord. To the best of our knowledge, this is the first report of LSC after RRP for prostate cancer in the English literature.