Four Al-Ti-Mg mixed oxide supports were synthesized by the sol-gel method, adding different MgO loadings (0, 5, 10 and 20 wt.%). The samples were characterized by XRD, N-2 physisorption, FT-IR spectroscopy, FT-IR pyridine adsorption and UV-Vis DRS. The supports exhibited amorphous mesoporous structures, with average pore size between 3.8 and 7.8 nm and high specific surface areas (170-280 m(2) g(-1)); also, they showed a small presence of carbonates species and weak acid Lewis sites. Synthesized supports were co-impregnated with Ni, Mo and W salts at atomic ratio of Ni/[Ni + (Mo + W)] = 0.5. The catalysts were characterized by XRD, N-2 physisorption, UV-Vis DRS, Raman spectroscopy and TEM. Catalytic activity and selectivity were evaluated in the hydrodesulphurization (HDS) of dibenzothiophene (DBT) reaction; the results are discussed in terms of the MgO loading to the support. The best catalyst was NiMoW/Al-Ti-Mg catalyst with 5 wt.% of MgO, which showed better HDS activity than NiMoW/Al-Ti and a similar performance to that observed for the NiMo/Al2O3 reference catalyst. The activity observed could be correlated to the distribution of active phases on support as well as the pore size distribution. Also, it was found that the direct desulphurization (DDS) pathway was favoured by the trimetallic catalysts; however, the addition of a small loading of MgO (5 wt.%) showed a slightly gain towards the hydrogenation pathway (HYD). (c) 2012 Elsevier Ltd. All rights reserved.