This study was aimed at the possibility as an anti-tumor agent of a triterpenoid saponin (HaBC18) extracted from stem bark of Albizzia julibrissin in vivo. In order to evaluate anti-tumor activity of the HaBC18 in vivo, a tumor in the right side femoral muscle of Balb/c mouse was established by sarcoma 180 cells. The mouse bearing the tumor was orally medicated with the HaBC18, 4 times at a week interval. Compared to those of control groups bearing acites without agent treatment, the increased life span (ILS) of mouse bearing acites treated with the HaBC18 was 136.8% and the tumor inhibition ratio (TIR) of mouse bearing sarcoma was 39.0%. Apoptosis of the tumor cells in mice treated with HaBC18 were also observed by TUNEL assay. In conclusion, the HaBC18 has anti-tumor activity against the tumor induced by sarcoma 180 cells in mouse. (Cancer Prev Res 17, 163-168, 2012)