The early detection of prostate cancer is a life-saving event in patients harboring potentially aggressive disease. With the development of malignancy there is a dramatic reduction in the zinc content of prostate tissue associated with the inability of cancer cells to accumulate the ion. In the current study, we utilized endogenous zinc as a diagnostic biomarker for prostate cancer. We employed a novel fluorescent sensor for mobile zinc (ZPP1) to measure the concentration of zinc in thirty-nine patient samples of expressed prostatic secretion (EPS) in urine. We estimated the probability of classifying a subject as benign, low-risk, or high-risk as functions of the diagnostic test results using a non-informative prior Bayesian approach. Permutation tests and other non-parametric tests were also used. We demonstrated a significant trend in zinc score with disease and with disease risk (P = 0.03), and lack of a significant correlation between zinc score and PSA. We also showed that the proposed diagnostic is potentially superior to PSA for detecting high-risk disease. Considering that risk stratification represents an important unmet need, our method should advance the field of prostate cancer diagnostics and treatment planning.