Prostate cancer remains the second most commonly diagnosed cancer among the male population worldwide. Vitamin D deficiency has been linked to prostate cancer and its aggressiveness. Herein, we initiated a retrospective study to evaluate vitamin D status and monitoring in veterans with prostate cancer, and to examine the potential link between vitamin D and survival status and length of survival in this population. We found that veterans who were initially vitamin D deficient were significantly less likely to survive than those who were not initially deficient, and that both initial and follow-up vitamin D deficiency were associated with decreased likelihood of survival after prostate cancer diagnosis. We recommend that vitamin D deficiency be replaced in veterans with prostate cancer.