Apogossypol, a gossypol derivative, is a novel small‑molecule inhibitor of the Bcl‑2 family proteins and has been demonstrated to have anti‑tumor activities. Prostate cancer is the most common malignancy in males, for which chemotherapy is the usual treatment option in clinical practice. The aim of the present study was to investigate the growth inhibitory effects of apogossypol on prostate cancers in vitro and in vivo. An MTT assay and a colony formation assay were used to assess the anti‑survival and anti‑proliferation effects of apogossypol in LNCaP cells. Immunofluorescence was performed in order to detect the expression levels of apoptosis‑associated proteins in xenograft tumors following apogossypol treatment. Apogossypol exerted strong anti‑tumor effects on LNCaP cells in a dose‑dependent manner. Furthermore, immunofluorescence revealed that apogossypol inhibited the growth and proliferation of prostate cancer cells by downregulating Bcl‑2 protein expression and activating caspase‑3 and ‑8. In addition, the in vivo study indicated that apogossypol significantly inhibited tumor growth in a dose‑dependent manner with reduced toxicity compared with gossypol. In conclusion, the present study indicated that apogossypol effectively inhibited the growth and proliferation of prostate cancer cells and may be a potential agent for prostate cancer therapy.