Purpose: This study assessed the relationship between newly developed normal-tension glaucoma (NTG) and androgen deprivation therapy (ADT) in patients with prostate cancer. Materials and Methods: A retrospective population-based cohort study was performed. During the period between 2008 and 2017, a total of 218203 prostate cancer patients were identified in a nationwide claims database in the Republic of Korea. The final analysis included 170874 patients (42909 in the ADT group, 127965 in the control group) after applying the inclusion and exclusion criteria. The incidences of NTG according to ADT duration were compared with controls. Exact matching was conducted to adjust comorbidities between cohorts. Cox proportional hazard regression models were performed after controlling for latent confounding factors, and adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of NTG according to ADT were obtained. Results: In the matched cohort, the ADT group was associated with a significantly reduced risk of NTG in multivariable analysis compared to the control group. The risk of NTG decreased in patients who underwent ADT for less than 2 years (HR=0.824; 95% CI, 0.682–0.995; p=0.0440) and in those using ADT over 2 years (HR=0.796; 95% CI, 0.678–0.934; p=0.0051), compared to the controls. Conclusion Medical castrations for patients with prostate cancer results in a lower incidence of newly diagnosed NTG compared to no ADT. These findings suggest that testosterone may be involved in the pathogenesis of NTG.