|Abstract||We examined the antioxidant and antimicrobial activities of quince (Cydonia oblonga Miller) leaf methanol extract of Tunisian variety Commune. Chromatographic characterization of the leaf extract using HPLC-MS/MS revealed the presence of 9-phenolic acids and flavonoids. Among these polyphenols, 6-were identified, one as caffeoylquinic acid (4-O-caffeoylquinic acid), two as quercetin heterosides (quercetin-3-O-rutinoside and quercetin-3-O-galactoside), and three as kaempferol heterosides (kaempferol-3-O-rutinoside, kaempferol-3-O-glycoside and kaempferol-3-O-glucoside). The leaf methanol extract had DPPH (2,2-diphenyl-1-picrylhydrazyl) friiee radical-scavenging activity, inhibited the pre-formed radical ABTS. + (2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid) and also inhibited the formation of hydroxyl radical. The antimicrobial potential of quince leaf extract was also tested against 8-pathogenic bacteria by disc diffusion method (namely, Salmonella typhimurium (ATCC 14028), Escherichia coli (ATCC 6538), Enterococcus faecalis (ATCC 29212), Enterococcus faecium (ATCC 19434), Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus agalactiae, Bacillus subtilis, and Saccharomyces cerevisiae).