Prostate cancer is currently the most commonly diagnosed malignancy, and the second leading cause of cancer-related death, in men in the United States. Most deaths from prostate cancer are due to metastatic disease that no longer responds to androgen deprivation. There have been several advances within the last decade leading to the approval of new agents for treating patients with castration-resistant prostate cancer. However, these agents can have significant side effects, and the average survival benefit from chemotherapy has been modest. Results from several clinical trials have suggested that immune-based therapies may have clinical benefits in patients with prostate cancer with significantly fewer adverse events. These new therapies, however, pose new potential benefits and risks. We review here two cellular immunotherapies furthest in clinical development for prostate cancer, and discuss the potential challenges to the treating oncologist with the possible advent of these new therapies.