A part of our continuing search for antiplasmodial compounds from Indonesian marine sponge, two steroidal alkaloids, epoxysarcovagenine-D (1) and epoxyepapakistamine-A (2), have been isolated from the ethyl acetate extract of the Indonesian marine ponge, Xestospongia sp. Their structures were identified on the basis of spectroscopic data analysis and by comparison with published spectroscopic and physicochemical properties data. Compounds 1 and 2 were isolated first time from marine sponge, Xestospongia sp., and showed strongest plasmodial activity against Plasmodium falciparum 3D7 strain with IC50 values of 0.013 and 0.158 mu M, respectively.