This study was aimed at hybrid nanocatalysts to reduce emissions of a diesel engine fueled with nanocatalyst biodiesel blends. Biodiesel was produced from Prosopis juliflora oil by the transesterification process. The nanocatalyst having cerium oxide on multiwall carbon a nanotube was investigated using biodiesel blends at two concentrations (50 and 100 ppm).The results revealed that the high surface area of the nanoparticles and their proper distribution along with catalytic oxidation reaction resulted in significant overall reductions in the emission. More specifically, all pollutants, i.e., CO, HC, and NOx, and smoke opacity were reduced when compared to B20.