Background: Prostate cancer (PCa) represents a common disease in men aged >65 years. The role of physical activity (PA) in patients at risk or diagnosed with PCa represents an evolving issue. We aimed to summarize available evidences about the impact of PA on the pathophysiology and clinical outcomes of PCa. Methods: We performed a narrative review. Evidences about the role of PA in elderly patients in terms of PCa biology, epidemiology, oncological and functional outcomes, as well as in terms of impact on the outcomes of androgen deprivation therapy (ADT) were summarized. Results: Potential pathophysiological pathways hypothesized to explain the benefits of PA in terms of prostate carcinogenesis include circulating levels of Insulin-like growth factor-1 (IGF-1), oxidative stress, systemic inflammation, sex hormones, and myokines. Clinically, emerging evidences support the hypothesis that PA is associated with decreased PCa risk, improved PCa-related survival, improved functional outcomes, and reduced ADT-related adverse events.