In order to elucidate the effect of support composition and preparation method on catalytic properties and hydrodesulfurization activity, a series of NiMo/Al2O3-ZrO2 nanocatalysts with various ZrO2 contents were synthesized by using impregnation and sonochemical methods. The samples were characterized by using BET, XRD, FESEM, PSD, EDX and FTIR techniques. The results indicated that in the samples with low ZrO2 contents, zirconia particles existed as amorphous phase which confirmed the existence of stronger interaction between metal oxides. The nanocatalyst synthesized by sonochemical method resulted in smaller particles with more uniform distribution compared to impregnation method. The catalytic activity of synthesized nanocatalysts was measured in a stirred slurry-tank reactor at atmospheric pressure and 160 degrees C using thiophene as the sulfur containing model compound. The catalytic activity of the sonochemically synthesized nanocatalysts was higher than those synthesized by impregnation method. ZrO2 loading led to a catalyst with higher activity compared to the zirconia free catalyst. Maximum catalytic activity was obtained with the zirconia content of 15 wt.%. Further introduction of zirconia led to a decrease in catalytic activity due to the formation of large ensembles on nanocatalyst surface. Furthermore, this work suggested a reaction path to reveal the mechanism of thiophene hydrodesulfurization over NiMo/Al2O3-ZrO2 nanocatalyst (C) 2014 Elsevier B.V. All rights reserved.