Quercetin is a flavonoid agent detected in fruits and vegetables with anti-inflammatory, antioxidant, and anticancer effects. This flavonoid can suppress cell cycle transition and induce apoptosis in neoplastic cells. Therapeutic effects of quercetin have been assessed in diverse cancers including prostate cancer through the establishment of in vitro and in vivo experiments. Moreover, this agent might prevent the initiation of this type of cancer as it indirectly blocks the activity of promoters of two important genes in the pathogenesis of prostate cancer i.e. androgen receptor (AR) and prostate specific antigen (PSA). Several in vitro investigations have identified the differential influence of quercetin on normal prostate cells versus neoplastic cells, emphasizing its specific cytotoxic effects on cancerous cells. The most appreciated route of quercetin effect on prostate cancer cells is the detachment of Bax from Bcl-xL and the stimulation of caspase families. Besides, quercetin might enhance the effects of other therapeutic options against prostate cancer. For instance, a combination of TNF-related apoptosis-inducing ligand (TRAIL) and quercetin has been recommended as a novel modality for the treatment of prostate cancer. These kinds of strategies might overcome resistance to apoptosis in cancer cells. In the current paper, we summarize the recent data about the preventive and therapeutic influences of quercetin in prostate cancer.