In this study, the effect of neat lemongrass oil [1]-diesel blends on the performance, combustion and emission characteristics of a direct injection diesel engine was investigated with different injection timings of 21° (retarded), 23° (normal) and 27° (advanced) bTDC positions by using four different fuel blends of diesel, LGO25, LGO50 and neat lemongrass oil. The experimental results show that maximum cylinder pressure and heat release rate increased with advanced fuel injection timing for all test fuels. There was a reduction in BSFC and significant improvement in the brake thermal efficiency (BTE) with advanced injection timing. Emissions from the diesel engine such as smoke and hydrocarbon (HC) were reduced but NO X emission was very high with advanced injection timing compared with other injection timings. When the injection timing is advanced, ignition delay increases, which leads to the more prominent initial phase of combustion in the premixed region. In the light of the experimental results, the optimal injection timing determined for LGO-diesel blends was found to be 27° bTDC.