Phytochemical characterization of a commercial herb sample supplied as Smilax ornata Lem. (sarsaparilla) led to the isolation of five steroidal saponins, including two new furostanol saponins sarsaparilloside B (1) and sarsaparilloside C (2), whose structures were elucidated via a combination of multistage mass spectrometry (MS(n)), 1D and 2D NMR experiments, and chemical degradation. The previously unreported spectroscopic characterization of sarsaparilloside (3), Δ(20(22))-sarsaparilloside (4), and parillin (5) is also provided. The antiproliferative activity of the isolated saponins was compared in six human cell lines derived from different tumor types and one of the structures (2) was particularly active against the HT29 colon tumor cell line.