We examined the antiproliferation effect of Jaceosidin (4', 5, 7-trihydroxy-3', 6-dimethoxyflavone) isolated from the herb of Artemisia vestita Wall on several human cancer cell lines. Jaceosidin significantly reduced the proliferation of CAOV-3, SKOV-3, HeLa, and PC3 cells in a concentration-dependent manner. A time-dependent inhibition was also observed in CAOV-3 cells by Jaceosidin. By flow cytometric analysis, we found that Jaceosidin treatment resulted in an increased apoptosis in CAOV-3 cells. The cells treated with Jaceosidin exhibited a decreased mitochondrial membrane potential. Jaceosidin also increased the level of cleaved caspase-9 and induced the cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP), while caspase-3 inhibitor Z-DEVD-FMK significantly reversed the proapoptotic effect of Jaceosidin in CAOV-3 cells. Moreover, Jaceosidin elevated the level of cytochrome c in cytosol. These findings suggest that the anticancer effect of Jaceosidin may be contributed by an induction of apoptosis involving cytochrome c release from mitochondria to cytosol.