Two new triterpene glycosides, namely holothurin $A_3$ (1) and $A_4$ (2) were isolated from the methanol extract of the sea cucumber, Holothuria scabra, with their structures elucidated from the spectroscopic evidence (1D NMR, 20 NMR, ESI-MS and HRESI-MS). Compounds 1 and 2 were found to be strongly cytotoxic to both cancer cell lines, KB and Hep-G2, with 50% inhibitory concentrations $(IC_{50})$ of 0.87 and $0.32{mu}g/mL$ (for compound 1) and of 1.12 and $0.57{mu}g/mL$ (for compound 2), respectively.