Highly and uncontrolled cell proliferation on cancer cells may boost ROS level intracellular accumulation up significantly. Sappan heartwood (Caesalpinia sappan L.) have been known to have cytotoxicity effect toward several cancer cells. This research was conducted to develop Caesalpinia sappan L. heartwood ethanolic extract (CSE) as chemopreventive agent which can be used as cancer therapy, looked from antioxidant and anti-senescence activity toward 4T1 breast cancer cell. CSE was obtained through maceration using ethanol 70% as solvent. Cytotoxicity activity of CSE was done by using MTT assay with IC50 as parameter. This IC50 was used as basic to the next assay, ROS assay by using DCFDA staining flowcytometry to look ROS level intracellular of CSE toward 4T1 cell and senescence assay by using senescence associated β-galactosidase (SA β-gal) assay with % cell senescence as their parameter. CSE toxic to 4T1 cell that proved from IC50 value of 25 µg/mL. Single treatment of CSE on concentration 12,5; 25; and 37.5 µg/mL able to suppress ROS level intracellular. If compared with untreated cell, single treatment of CSE on concentration 6 and 12 µg/mL showed % cell senescence not significantly different. Based on this result, CSE is cytotoxic, has antioxidant and antisenescence activity, so it has great potential to developed as chemoprevention agent on cancer therapy.Keywords : Caesalpinia sappan L., 4T1 breast cancer line, Reactive Oxygen Species (ROS), anti-senescence