Objective: To evaluate the antitumor activity both in vitro and in vivo of saponin–phospholipid complex of Panax notoginseng. Methods: The in vitro cytotoxic effect of saponins extract and saponin–phospholipid complex against human lung cancer NCI-H460 and breast cancer cell lines BT474 was examined using MTS assay. For in vivo evaluation of antitumor potential, saponin and saponin–phospholipid complex were administered orally in rats induced mammary carcinogenesis by 7,12-dimethylbenz(a)anthracene, for 30 days. Results: Our data showed that saponin–phospholipid complex had stronger anticancer effect compared to saponin extract. The IC50 values of saponin–phospholipid complex and saponin extract for NCI-H460 cell lines were 28.47 μg/mL and 47.97 μg/mL, respectively and these values for BT474 cells were 53.18 μg/mL and 86.24 μg/mL, respectively. In vivo experiments, administration of saponin, saponin–phospholipid complex and paclitaxel (positive control) effectively suppressed 7,12-dimethylbenz(a) anthracene-induced breast cancer evidenced by a decrease in tumor volume, the reduction of lipid peroxidation level and increase in the body weight, and elevated the enzymatic antioxidant activities of superoxide dismutase, catalase, glutathione peroxidase in rat breast tissue. Conclusions: Our study suggests that saponin extract from Panax notoginseng and saponin–phospholipid complex have potential to prevent cancer, especially breast cancer.