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In this work, Co-promoted MoS2 catalysts supported on Al-modified mesoporous silica (HMS and SBA-16) have been prepared by the decomposition of ammonium tetrathiomolybdate and cobalt nitrate precursors in a H2S/H2 gas mixture. The effects of the support morphology and Al incorporation method (one-pot synthesis vs. support's grafting) on the catalyst activity were investigated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) conducted in a high-pressure batch reactor at 350 °C and total H2 pressure of 3.3 MPa. The physical and chemical characterization of the oxide precursors and spent catalysts was studied by a variety of several techniques (N2 adsorption–desorption, XRD, SEM, EDS, 27Al MAS NMR, Raman, TG/DTA and DRS UV–vis). The MoS2 phase of all catalysts exhibits similar size (about 2.8 nm) and stacking layers (4). Activity tests showed that CoAT/HMS-Al was most active and selective toward direct desulfurization (DDS) reaction pathway among the catalysts studied. Its catalytic response was similar to that of CoMo/γ-Al2O3 catalyst activated by reductive sulfiding. A linear correlation was found between DBT conversion at a reaction time of 5 h and the specific surface area and mean pore diameter of the catalysts. The best DBT HDS activity showed CoAT/HMS-Al catalyst having the best textural properties among the catalysts studied. Modification of SBA-16 with Al3+ ions by the one-step synthesis method rendered the catalyst more active in the HDS reaction than its modification by grafting. [ABSTRACT FROM AUTHOR]