Biodiesel production from waste vegetable used oils have a great interest as a substitute for petroleum diesel to reduce dependence on imported petroleum and provide an alternate and sustainable source for fuel with more benign environmental properties. In the present research biodiesel was prepared from three samples waste vegetable [mixture (sunflower 75% + soybean 25%), sunflower and cotton] oils (collected as wastes from Egyptian local restaurants) by transesterification. The reference used oils and the produced biodiesel samples of the studied oils were chemically characterized by gas chromatography mass spectrometry (GC–MS). All fatty acid, methyl esters (FAMEs) and other obtained compounds were identified by retention times and confirmed by comparing their mass fragmentation patterns with the GC-MS instrument library storage mass spectra. The percentage of obtained methyl esters of the studied oils before and after change to biodiesel was reported and discussed. Mixture (sunflower 75% + soybean 25%) waste oil have the best conversion to biodiesel with fatty acid, methyl ester content equal to 91.03% followed by cotton waste oil 89.56% then sunflower waste oil 86.92%. The importance of this work is to get benefits of the local environmental wastes as sources for renewable energy.