The present study aims to investigate the chemical composition, antimicrobial activity, antioxidant properties, and cytotoxic activity of extracts obtained from leaf samples that are discarded as waste products. For this purpose, two different green leaves were selected: one is the grape (Vitis vinifera) leaf, a by-product from the winemaking process, and the other is the cauliflower (Brassica oleracea, var. botrytis) leaf, which is a waste product of cauliflower, and they were subjected to related tests. Both leaf samples were extracted by water because of its easy accessibility and environmentally friendly properties. Leaf extracts were examined according to their total phenolic content and subjected to chemical characterization by Liquid chromatography-quadrupole time-offlight tandem mass spectrometry system. The promising antioxidant activities of the water-extracted leaf samples were authenticated through DPPH and ABTS assays. Antimicrobial and antibiofilm activities were examined against some Gram-positive (Bacillus cereus, Listeria innocua, and Carnobacterium divergens) and Gram-negative (Escherichia coli, Serratia liquefaciens, and Salmonella Typhimurium) strains, and two fungi (Saccharomyces cerevisiae and Candida albicans) species. Both tested leaf extracts showed a dose-dependent antimicrobial activity, while the antimicrobial activity of grape leaf extract was slightly higher. However, their activities against biofilm formation were varying in different bacterial and fungi species. The cytotoxic activity of the leaf extracts was examined on the mouse fibroblast cell (L929) line. According to the presented results, neither of the leaf extract samples used in the study showed any unwholesome effects on the cell line at any time point