Aromatic saturation is an important reaction for improving the cetane number of diesel streams. NiMo sulfide catalysts supported on alumina (Alu), silicaalumina (SiAl), and alumina-Y zeolite (AluZ) were prepared with similar dispersions and variable acidities. These catalysts were tested in the hydroconversion of tetralin, indan, decalins, and alkylbenzenes to evaluate the effect of the support acidity in the overall activity and the distribution of products. NiMo/Alu generated essentially hydrogenated products while the presence of an acid component on the support increased not only isomerization and cracking reactions but also hydrogenated compounds formation, especially on tetralin, indan, and butylbenzene hydroconversions over NiMo/AluZ catalyst. The better hydrogenation activity of NiMo/AluZ for these reactions was associated with the presence of strong acid sites that contribute to creating protonated species which would migrate to the sulfide phase. Such species would be easier to hydrogenate due to the lower stability of the aromatic ring.