This study investigates the influences of post-injection (PI) strategy and adding two concentrations (50 and 100 mg/l) of Cerium oxide (CeO2) nanoparticles to the diesel-castor oil (C30D) and diesel on engine performance, NOX emissions, and characteristics of PM. The adding CeO2 nanoparticles to the C30D and diesel were tested under with PI and W/O PI strategy. The results indicated that the BTE increased by 9.42% from the blends of C30D + CeO2 compared with diesel + CeO2 under with and without PI strategy. Furthermore, the BSFC decreased by 16.46% from C30D + CeO2 nanoparticles compared with diesel + CeO2 nanoparticles. The cylinder pressure and ROHR increased with addition of CeO2 nanoparticles to the C30D compared to the C30D, diesel, and diesel + CeO2 under different PI strategy. For the same CeO2 concentration, the results showed that the NOX emissions decreased by 10.64% when adding 100 mg/L of CeO2 to the C30D compared with diesel + CeO2 nanoparticles by 8.73%. The adding 50 and 100 mg/L of CeO2 to the C30D reduced the concentration of PM by 28.62 and 42.72%, respectively, compared C30D without additives. Besides, the adding both concentrations of CeO2 to the diesel decreased the concentration of PM by 16.74 and 24.83%, respectively, compared without additives into the diesel fuel. It is found that the size of primary particles (d(po)) slightly increased with addition of CeO2 nanoparticles to the C30D and diesel under with and W/O PI strategy. The data of this experiment revealed that introduce the PI strategy and 100 mg/L of CeO2 nanoparticles gives positive effect on engine performance, NOX emissions, and total concentration of PM.