The production of greenhouse gases such as carbon dioxide causes global warming and many other environmental problems. Diesel engines are widely used due to their higher output torque value, better thermal efficiency and durability compared to gaso-line engines. Because of rapid consumption and mitigation of diesel as a fossil fuel, bio-diesel has recently received significant attention as a renewable energy source. There are several sources in order to produce biodiesel. Animal fats, inedible vegetable oils, waste oils and other low-value bioenergy raw materials are suitable sources for biodiesel pro-duction as they are renewable and have no impact on food safety. In this study, CeO2 nano additives at concentrations of 50 ppm and 75 ppm were added to cottonseed based biodiesel. The experiments were conducted at 4 different load conditions on a 3-cylinder water-cooled diesel engine. According to the test results, it was observed that with increasing nano additive concentration, thermal efficiency was increased and spe-cific fuel consumption was reduced. As well as, the results indicated that CO and soot emissions were reduced, while NOx emissions were increased due to the improvement of the combustion performance caused by CeO2 nanoparticles.