The aim of this study is to investigate the effects of nanoparticles type, nanoparticles size, and droplet size on the ignition probability of the diesel fuel. Also, the effect of metal oxide nanoparticles on the ignition delay of diesel fuel droplets is studied. A series of hot plate ignition tests are conducted for diesel fuel with and without Al2O3, TiO2 and Fe3O4 nanoparticles at different concentrations (up to 0.05 wt.%). The experimental results show that the ignition probability of the diesel fuel significantly increases in the presence of metal oxide nanoparticles. The ignition probabilities of diesel/Al2O3 and diesel/Fe3O4 nanofuels are almost similar and higher than that of diesel/TiO2 nanofuel. Results for diesel/Al2O3 show that the nanoparticle size does not affect the ignition probability of nanofuel. Moreover, results indicate that the ignition probability decreases by increasing the droplet size. Investigations show that the ignition delay for diesel fuel droplets decreases in the presence of Al2O3 nanoparticles.