¹Department of Pharmacognosy and Medicinal plants, College of Pharmacy, University of Baghdad, Iraq DOI : 10.29228/jrp.741 Aims of study are identification, isolation, identification and determination of some type bioactive constituents presents in Sanseveria trifasciata (S.trifasciata) with assessment of the effectiveness of ethyl acetate fraction roots and leaves as antiproliferative agents against breast cancer (MDA-MB-231) cell lines. The roots and leaves of S. trifasciata were macerated in n-hexane for defatting, then the defatted components were extracted using a hot extraction technique with 85% aqueous ethanol, and the extracted parts were fractionated first with chloroform, ethyl acetate, and then n-butanol. A fraction of ethyl acetate is analyzed by analytical high performance liquid chromatography (HPLC) to determine its component. Assessment of its cytotoxic activity was performed using the MTT (3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide) assay. for 24 hours, multiple concentrations of extracts are used to treat the breast cancer (MDA-MB-231) cell line. After 72 hours of treatment, media were removed and cell viability was calculated. The qualitative HPLC analysis showed that the ethyl acetate fraction of roots contains apigenin, quercetin, chlorogenic acid, luteolin, catechin, and caffeic acid but did not contain kaempferol. On the other hand, the ethyl acetate fraction of leaves contained apigenin, kaempferol, chlorogenic acid, luteolin, and catechin but does not contain quercetin. A cytotoxic study (MTT assay) showed that the IC50% for roots was 89.83 μg/ml and the IC50% for leaves was 77.6 μg/ml. Ethyl acetate extracts of S. trifasciata from both roots and leaves showed anti-breast cancer cell lines through inhibition of proliferation. However, leaves showed a more inhibitory effect at the lower concentration than roots. Keywords : Cytotoxic effect; Ethyl acetate fraction; HPLC; MDA-MB-231 cell line; S.trifasciata