This paper investigated the role of emission characteristics of a diesel engine when zirconium oxide (ZrO2) nano additive blended with caulerpa racemosa oil methyl ester (CROME) is used as a fuel. Biodiesels can be produced from caulerpa racemosa oil by the transesterification process. The ZrO2 was added to B20 blends at the dosages of 50 ppm and 100 ppm. The fuel properties of B20, B20ZrO(2)50, and B20ZrO(2)100 were studied and compared according to ASTM standard test methods for biodiesel. Tests were performed at full-load compression ignition engine. The acquired data were studied for various parameters, such as exhaust emission of HC (hydrocarbon), CO, NOx, and smoke opacity.