Less than 100 cases of prostate carcinosarcoma have been described in published studies. Most of these cases describe symptoms due to bladder outlet obstruction that typically results in transurethral resection of the prostate. Our patient presented with tenesmus and stranguria due to prostate carcinosarcoma that developed years after being treated with external radiation and androgen deprivation for prostate adenocarcinoma. Because of the patient's escalating symptoms, a pelvic exenteration with creation of urinary and fecal diversions was performed. Despite the dismal survival associated with prostate carcinosarcoma, palliative surgical extirpation can be successful in patients with debilitating pain.