Currently, the options available for the treatment of various cancers including breast cancer, are associated with several limitations such as severe toxicity, drug resistance, poor prognosis, and high risk of recurrence. Therefore, there appears to be an increasing interest and necessity in investigating various phytochemicals from natural sources for a superior and safer alternative treatment strategy. The bioactive phytochemical alpha (α) and beta (β)-asarone from Acorus calamus is a traditional medicine system that has been shown to have anti-tumor and chemo-inhibitory activities in numerous preclinical studies both in vitro and in vivo.Various experimental studies with human malignant cell lines and animal models have also confirmed the anti-tumor and anticancer activities of β-asarone. In this study, we aimed to investigate the anti-cancer effects of β-asarone alone or together with etoposide buy measuring cellular responses such as cell viablity, cell cycle arrest and apoptosis using breast cancer cell line MCF-7 cells. In order to get insight in to the mechanism, we also tested the expression of of NF-κB / p65 activity and the expression of Bcl-2 family member pro-apoptotic Bax protein together with p53 and p21 activities in response to β-asarone alone or together with etoposide treatment. As a result, it was concluded that the use of β-asarone alone in breast cancer cells is effective in reducing cell viability, but when used together with Etoposide, it does not cause a synergistic effect. Here we suggest that that in particular activation of NF-kB/p65 may be lead resistance to etoposide treatment.