Melastoma malabathricum L. is a type of plant naturally grows in Kalimantan that has medicinal properties. Ethanolic extract of M. malabathricum L. flower has quercetin and kaempferol contents that have antioxidant and anticancer activities. But the antioxidant and cytotoxicity activities of M. malabathricum L. fruit ethanolic extract were not known. This study measured the quercetin and kaempferol level in M. malabathricum L. fruit ethanolic extract using HPLC MS/MS, antioxidant activity using DPPH method, and cytotoxicity activity using Brine Shrimp Lethality Test (BSLT) method. Results showed the level of quercetin and kaempferol from M. malabathricum L fruit ethanolic extract are 67.78 μg/g and 43.52 μg/g, respectively. Beside, the antioxidant activity with by IC50 was 16.82±0.24 ppm and 7.38±0.41 ppm. The cytotoxicity activities of M. malabathricum L. fruit ethanolic extract and quercetin are shown by the LC50 of 313.44 ppm (95%CI 283.97-344.43) and 37.24 ppm, respectively. Keywords: M. malabathricum L- quercetin- kaempferol- antioxidant- cytotoxicity