Background & aim: Breast cancer is the most common cancer among women. Today, compounds derived from medicinal plants are used in the treatment of various cancers. Despite reports of antitumor effects on some Stachys species, the activity of Stachys setifera extract on breast cancer cell lines has not been studied. Therefore, the aim of the present study was to investigate the effect of hydroalcoholic extract of Stachys setifera on MCF-7 cancer cell proliferation.