Cannabis sativa L., Cannabaceae, has been used as a herbal medicine for several thousand years in many cultures and it has more than 540 metabolites that provide therapeutic effects. Cannabinoids are the major compounds derived from the Cannabis species. There are over 120 isolated and identified cannabinoids from C. sativa and (−)-cannabidiol is one of the most well-researched among them. Recent studies have focused on the expanding usage of cannabidiol in many therapeutic areas as well as cancer. Studies demonstrated a negative correlation between cannabidiol administration and the growth of various cancer types, including prostate cancer. However, the detailed mode of action of cannabidiol on prostate cancer remains unclear. In the present study, we investigated the molecular mechanism of cannabidiol prostate cancer cells. For this aim, we examined the effect of cannabidiol on autophagy, endoplasmic reticulum-associated degradation, endoplasmic reticulum stress, unfolded protein response, epithelial-mesenchymal transition, angiogenesis, and androgenic signaling in vitro. We found that cannabidiol remarkably inhibited autophagy. Also, it strongly induced unfolded protein response and endoplasmic reticulum-associated degradation mechanisms. Moreover, it exerted anti-cancer activity by reducing epithelial-mesenchymal transition and causing cell cycle arrest. Additionally, cannabidiol importantly disrupted androgenic signaling by affecting basal androgen receptor levels and inhibiting nuclear translocation of this receptor.