Despite the progress in cancer therapies such as chemotherapy and radiation, its eradication remains as unattainable dream for the patients and doctors. Recently, using supplementary agents such as herbal medicine with fewer side effects seems efficient and attractive. Therefore, the purpose of the present study is to investigate if the ethanolic extract of P.oleracea has cytotoxicity and apoptosis induction on oral epithelial cancer cell line (KB cell line). The KB cells were cultured with different doses of ethanol extract (0, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500 μg­/­ml) for 24, 48 and 72 hours and the cytotoxicity and cell survival were measured through MTT and trypan blue respectively. In addition, the cells stained with Hoechst reagent to study apoptosis induction after their treatment with 4000, 4500 and 5000 μg­/­ml of P.oleracea ethanolic extract at 24, 48 and 72 hours. Our findings showed that P.oleracea had time and concentration dependent anticancer effects on KB oral cancer cell line (P <0.05), so that there was a significant difference between all experimental and the control group. In addition, 1500 μg­/­ml P.oleracea extract was considered as IC50 level according to MTT assay. Also, condensation, shrinkage and breakdown of the cells nuclei confirmed the apoptosis induction at 4000, 45000 and 5000 μg­/­ml concentration. It seems that ethanolic extract of P.oleracea leads to inhibit cancer cells growth and induce cell death through apoptosis at all concentrations. However, several preclinical or clinical studies should be designed to prove its safety, effectiveness and mechanisms.