Cell apoptosis induction and metastasis suppression in human breast cancer cell, MDA-MB-231, were studied to assess the potential of Cirsium setidens extract (CSE) on breast cancer treatment. Cell viability and metastasis analysis using MDA-MB-231 confirmed CSE significantly inhibited the growth and proliferation of cancer cell without suppressing normal cell growth in the range of 0.25 to 0.5 mg/mL of CSE. To analyze the anticancer effect of CSE, the expressions of major genes related to in the apoptosis, including p53, AMPK-α, Bcl-2, and Bax were analyzed by reverse transcription-polymerase chain reaction. The expressions of AMPK-α, p53, and Bax increased by 45, 43, and 68%, respectively, while the expression of Bcl-2 decreased by 12%, showing that CSE treatment induced apoptosis of MDA-MB-231. The major compound of CSE was identified as rhoifolin, a type of flavone, through analysis using LC-MS/MS. Our findings confirmed that rhoifolin, known to possess a variety of significant biological activities, could be obtained from C. setidens and used as an effective natural compound to suppress breast cancer.