MoS2-amorphous silica-alumina (MoS2-ASA) bifunctional catalysts for slurry-phase hydroconversion of the model reactants phenanthrene and decalin were prepared using three distinct methodologies. The MoS2-ASA catalysts were prepared by (i) a mechanical mixture of MoS2 (prepared separately) and ASA, which were mixed directly in the reactor for the hydroconversion test (MM catalyst); (ii) in situ sulfidation of the molybdenum precursor in the presence of the ASA, both dispersed in the phenanthrene-decalin reaction mixture (IS catalysts); and (iii) impregnation of molybdenum octoate onto ASA, followed by thermal treatment to chemically link the Mo precursor to the ASA surface followed by sulfidation prior to the catalytic test (IMP catalyst). Among the three preparation methods, the MoS2-ASA catalysts prepared in situ (IS) had the highest MoS2 dispersion and degree of sulfidation and yielded the highest hydrogenating activity at the lowest Mo catalyst content (2.9Mo-ASA). Although the MoS2 blocked Brønsted acid sites decreasing the ASA acidity, especially in IS and IMP catalysts, at the low Mo concentrations required with the IS methodology, most of the acidity was retained. In addition, in the case of IS catalysts, MoS2 particles were also found dispersed in the slurry feed independently of the ASA. Consequently, the IS catalyst retained the advantages of the unsupported MoS2 with the additional functionality of the acid component of the bifunctional catalyst; hence, conversion was promoted due to both hydrogenation and hydrocracking reactions. These observations suggested that the bifunctional MoS2-ASA catalysts prepared in situ promotes hydrocracking reactions at lower temperatures reducing the severity of reaction conditions and limiting coke formation in slurry-phase hydroconversion.