Angiotensin Ⅱ (Ang Ⅱ) stimulates tumor growth and angiogenesis in some solid cancer cells, but its anti-apoptosis role in breast cancer remains unclear. To address this issue, we investigated the effect of Ang Ⅱ on adriamycin-induced apoptosis in breast cancer MCF-7 cells. Treatment of human breast cancer MCF-7 cells with adriamycin, a DNA topoisomerase Hα inhibitor, caused apoptosis. However, cells pretreated with Ang Ⅱ were resistant to this apoptosis. Ang Ⅱ significantly reduced the ratio of apoptotic cells and stimulation of phospho-Akt-Thr308 and phospho-Akt-Ser473 in a dose-dependent and time-dependent manner. In addition, Ang Ⅱ significantly prevented apoptosis through inhibiting the cleavage of procaspase-9, a major downstream effector of Akt.The Ang Ⅱ type 1 receptor (AT1R) was responsible for these effects. Among the signaling molecules downstream of AT1R,we revealed that the phosphatidylinositol 3-kinase/Akt pathway plays a predominant role in the anti-apoptotic effect of Ang Ⅱ. Our data indicated that Ang Ⅱ plays a critical antiapoptotic role in breast cancer cells by a mechanism involving AT1R/phosphatidylinositol 3-kinase/Akt activation and the subsequent suppression of caspase-9 activation.