Asterosaponin 1, a new cytostatic agent from starfish, possesses several bioactivities including an antitumor effect. The aim of this study was to investigate the potential anti-proliferative and pro-apoptotic activity of asterosaponin 1 in A549 human lung cancer cells, as well as the potential mechanisms. The results showed that asterosaponin 1 inhibited the proliferation of A549 cells in a dose-dependent manner, and the cytostatic activity resulted from the induction of apoptotic cell death. Asterosaponin 1 increased ER dilation and cytosolic Ca2+ concentration, and enhanced the expression of the ER molecular chaperones GRP78 and GRP94 in a dose- and time-dependent manner. In addition, asterosaponin 1 treated A549 cells exerted increased expression and activity of CHOP, caspase-4 and JNK, three essential ER-associated apoptotic molecules. In summary, these results demonstrated that asterosaponin 1 inhibits the proliferation of A549 cells through induction of ER stress-associated apoptosis, making asterosaponin 1 a candidate new anticancer drug for lung cancer therapy.