Coptosapelta flavescens has been reported to possess various biological activities, particularly antioxidant and cytotoxicity effects. This study evaluated the antioxidant and cytotoxic properties of fractionated extracts against the MDA-MB-231 breast cancer cell line. The fractions were obtained by solvent partitioning with increasing polarity, namely n-hexane, chloroform, dichloromethane, ethyl acetate, and methanol.Total polyphenol content was determined using the Folin–Ciocalteu method, antioxidant activity by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay (DPPH), and cytotoxicity by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT). Polyphenols were primarily distributed in the ethylacetate, chloroform, and dichloromethane fractions, with their concentrations of (186.65, 211.95, and 219.66) µg GAE/mg, respectively. These fractions also exhibited antioxidant capacity with IC50 values of (15.24, 12.27, and 11.59) µg/mL, respectively. Furthermore, they demonstrated cytotoxic activities against MDA-MB-231 cells, reducing cell viability by 50% after 72 h at concentrations of (88.12, 106.67, and 104.72) µg/mL, respectively. These findings indicate that these fractions are promising sources of bioactive compounds with antioxidant and cytotoxic potential.