In the present investigation a fast, convenient and environment friendly method has been used for the synthesis of copper oxide nanoparticles by biologically reducing 1 mMCuSO4 solution with extract of 2 % (m/v) of Khat (Catha edulis) under optimum conditions (pH of 11). The formation of copper oxide nanoparticles was indicated by the color changes from colorless to light green then to greenish yellow and finally, after days, to brown precipitate. Biosynthesized nanoparticles were also characterized by UV-Visible and FT-IR spectroscopies. The kinetics of the reaction was studied using UV–Visible spectrophotometer.The reduction process was simple and convenient to handle and was monitored by UV-Visible spectroscopy that showed surface plasmon resonance at 333 nm, which is very much different from 294 nm of the pure Khat extract.This has clearly revealed the formation of copper oxide nanoparticles. The presence of active flavanoids, phenolic groups, tannins, alkaloids, Glycosides and carbohydrates whichwere in the biomass of the Khat extract before and after reduction was identified using qualitative screening methods (observing the color changes) and FT-IR spectroscopy. These biologically synthesised copper oxide nanoparticles were tested for their antimicrobial activity against two human pathogens, i.e Salmonella typhimurium and Escheria Coli. They were found to have significant effect in controlling the growth of the human pathogens with an average zone of inhibition of 10 mm. Therefore, using Khat for the synthesis of the copper oxide nanoparticle, applied in different fields, is another possible way.