Injection timing is a vital factor which governs the emissions and performance characteristics of the engine. This work portrays the effect of injection timing (IT) on cerium oxide nano particle doped palm biodiesel (20%vol) and diesel (80%vol) blends. Palm biodiesel is found to be a promising alternative to the petroleum diesel fuel owing to their similarity in physical and chemical properties. Addition of cerium oxide nano particle is carried out at 30 ppm, 60 ppm and 90 ppm. The modified fuels are introduced in reducing injection timing of 19°, 21° and 23° bTDC. A four-stroke, vertical, air-cooled, single cylinder, diesel engine is employed in this study. The performance characteristics (BSFC, BTE) improved for fuel blends at IT=23° bTDC. Further, results also revealed a significant reduction in emissions CO, NOX, HC emissions at IT=23° bTDC.