Increasing global concern because of air pollution produced by diesel engine has shown an immense interest in the ecofriendly fuels. In this context the non-edible vegetable oils and their methyl esters are considered as one of the alternate fuels. However since their direct utilization leads to high viscosity poor atomization and incomplete combustion along with higher NOx. In order to lessen this effect investigations are carried out on the performance and emissions of diesel engine by adding cerium oxide (CeO2) Nano-particles to the karanja biodiesel blends. This has shown improvements in engine performance and its emissions. © IAEME Publication.