Prostate cancer (PCa) is the most common genitourinary malignancy in men, with a multifactorial etiology influenced by genetic, environmental, and microbial determinants. Although the prostate was traditionally considered sterile, advances in microbiome research have challenged this view, revealing potential links between microbial communities and PCa development, progression, and treatment response. This review synthesizes evidence on the gut, urinary, seminal fluid, and prostatic microbiomes, highlighting their potential contributions to PCa pathogenesis and therapeutic outcomes. Key studies utilizing next-generation sequencing (NGS), whole-genome sequencing (WGS), PCR, and metagenomic analyses have identified specific bacterial and fungal taxa associated with Pca; however, findings remain inconsistent across methodologies and cohorts. Microorganisms such as Propionibacterium acnes and Pseudomonas spp. may modulate inflammation, immune responses, and resistance to androgen-deprivation therapy. Further research is required to determine whether microbial signatures can serve as reliable biomarkers for early detection, prognosis, or novel therapeutic strategies in PCa management.