Previous studies have shown that Pseudolaric acid B (PAB), a medicinal plant-derived terpenoid, is a promising chemopreventive or therapeutic agent against various types of cancer. However, less is known regarding its activity against prostate cancer. The objective of the current study is designed to determine the anti-prostate cancer effects of PAB. We demonstrated here that PAB was highly effective against both androgen-dependent (LNCaP) and androgen-independent prostate cancer cells (PC-3 and DU145) through the mechanisms involved in induction of G2/M cell cycle arrest, caspase-dependent apoptosis and autophagic cell death. Furthermore, PAB can greatly sensitize these two aggressive androgen-independent prostate cancer cells to ABT-737-induced cytotoxicity. Our findings suggest that PAB holds excellent potential as either novel chemopreventive agent or enhancer of therapeutic drug against prostate cancer. Copyright © 2012 John Wiley & Sons, Ltd.