Objective: The aim of the present study is to study the correlation between urinary cortisol and melatonin metabolites and prostate cancer. Method: Patients with a histologically confirmed new prostate carcinoma with no previous malignancies have been included in the study as “cases.” Healthy individuals who applied to check-up and sleep disorder polyclinics were included as the healthy control group. Serum prostate-specific antigen (PSA), urinary melatonin sulfate, and cortisol levels in the first-morning spot urine samples were measured during the admission and diagnosis for all participants. Results: A total of 180 patients with a proven pathology of prostate adenocarcinoma and 240 healthy males participated in the study as the control group. When compared with the control group, significantly lower urinary melatonin sulfate levels (49.85±46.58) ng/mg vs. (64.25±66.75) ng/mg, p = 0.003) and significantly lower melatonin sulfate/cortisol (M/C) ratios (2.38 ± 3.20 vs. 5.28 ± 15.32, p <0.001) (respectively) levels were found in the patients. Subjects who had high M/C ratios and urinary melatonin-sulfate were less exposed to risk of prostate cancer at a statistically significant rate than those with lower urinary melatonin-sulfate or M/C ratios. We also discovered that subjects with a low M/C ratio and preoperative PSA levels above 10 ng/mL were 3.58 times more likely (95% CI = 1.58–8.12) to develop prostate cancer than those with a high M/C ratio and preoperative low PSA (<10 ng/mL). Conclusion: We concluded that there was association between lower morning melatonin sulfate levels or M/C ratio and the risk of prostate cancer. Moreover, patients who had both low PSA levels and M/C ratios higher than 10 ng/mL were much more exposed to advanced (end-stage) disease and prostate cancer.