The study investigates the effect of aluminium oxide nanoparticles as additive to pongamia methyl ester (PME) blends on performance, combustion and emission characteristics of a single cylinder direct injection diesel engine operated at constant speed at different operating conditions. The test fuels are indicated as B25 (75% diesel and 25% PME) and B25A50 (75% diesel and 25% PME and 50 ppm Aluminium oxide nanoparticles) and B25A100 (75% diesel and 25% PME and 100 ppm Aluminium oxide nano particles) respectively. The results indicate that the brake thermal efficiency for aluminium oxide nanoparticles blended pongamia methyl ester increases slightly while brake specific fuel consumption (BSFC) decreases when compared to other blends. The carbon monoxide (CO), unburnt hydrocarbon (HC) and smoke emission marginally decreases as compared to mineral diesel. Oxides of nitrogen (NOx) emissions are higher for aluminium oxide nanoparticles blended pongamia methyl ester. Higher cylinder gas pressure and higher heat release rate were observed for aluminium oxide nanoparticles blended pongamia methyl ester. From the study, the blending of aluminium oxide nanoparticles in biodiesel blends produces most promising results in engine performance and also reduces the harmful emission from engines. (C) 2017 Elsevier Ltd. All rights reserved.