The effect of two different kinds of biodiesel on performance characteristics and emissions of turbojet engine is investigated experimentallyand compared with the enginerecommended fuel (JetA-1)in this work. Two different kindsof biodiesel that areCotton Methyl Ester (CTME)andCorn Methyl Ester (CRME) and their blends of 10%, 20%and50% biodiesel/JetA1 by volumeare produced, characterizedand investigated experimentally in this study. The turbojet engine used in this work is fully equipped with pressure, flow, temperature, thrust and speedsensors inaddition to data acquisition system and control unit. Exhaust gas analyzer is usedat turbojet engineexitto measure the exhaust gasescomposition that areO2, CO, CO2,HC,NOx, and SO2. The performance characteristics of the engine areidentified byengine speed, static thrust, thrust-specific fuel consumption (TSFC)andthermal efficiency. The results show that biodiesel fuels have a higher density, kinematic viscosity, flash point and pour point than JetA-1 fuel, while, their calorific value, carbon and hydrogen contents is close to JetA-1 fuel. Moreover, the results show that the performance parameters for biodiesel are close to those for JetA-1. The static thrust for JetA-1 and alltested biodiesel fuel are very close while the TSFC for biodiesel fuel blends is lower than JetA-1. As expected the engineefficiency of biodiesel was higher than Jet A-1 because of the oxygen content on biodiesel chemical composition which leads to a leaner and more complete combustion. JetA-1 fuel has higher combustor exit temperature and exhaust gas temperature compared with biodiesel fuel blends.Biodiesel fuels and its blends have higher O2concentration in the exhaust compared.