Objectives: In this study, relative leukocyte telomere length (LTL) was investigated as a prognostic marker to evaluate association of LTL at the time of diagnosis and prostate cancer-specific survival, metastasis-free survival, overall survival, with castrate-resistant prostate cancer (CRPC). Materials and Methods: In this retrospective cohort study, pertinent data from 81 patients were collected. Patients underwent prostate cancer (PCa) treatment procedures determined by staging and current recommendation. Blood samples from suspected PCa patients were obtained before the initiation of diagnosis and treatment. LTL was determined by the quantitative polymerase chain reaction method. Relative LTL was compared to the main clinical outcome measures. Prostate cancer-specific survival, metastasis-free survival, overall survival and CRPC were calculated retrospectively, for a mean follow-up period of 30 months. Results: This analysis showed relative LTL was not associated with tumor stage, Gleason score, grade group, metabolic disease, or smoking. However, older age was significantly associated with short LTL (p < 0.001). All main outcomes were not associated with LTL. In contrast, a subgroup analysis of patients who underwent primary androgen deprivation therapy (ADT) showed a CRPC association with relatively long LTL (p = 0.039). To our knowledge, these results are novel and give further strength to our hypothesis that relative LTL might be used as a prognostic marker in PCa especially in patients who will receive primary ADT. Conclusion: Aging was significantly associated with relatively short LTL. There was no significant association between LTL in PCa patients at diagnosis and cancer-specific survival, metastasis-free survival, or overall survival. However, patients who underwent ADT treatment alone showed CRPC associated with relatively long LTL.