A heavy crude oil of 13 degrees API and a viscosity of 6100 cSt at 37.8 degrees C was used to study the effect of different hydrocracking catalysts at low severity conditions in a slurry-phase, batch reactor. The evaluated catalysts were Mo and Fe analytic grade oxides and ores (molybdenite, hematite, and magnetite) from different Mexican mine sites. The effect of the concentration of catalysts on heavy oil upgrading was studied in the range of 0-13 333 ppm of active metal (Mo or Fe). The results showed that the required minimum concentration of catalyst to obtain upgraded crude oil with suitable properties for transportation (API gravity > 16 and viscosity at 37.8 degrees C < 250 cSt) is 5000 ppm. At the evaluated operating conditions, coke formation is not observed and the selectivity toward gases is low. Mo showed better hydrogenation capacity than Fe, which is observed by an increase in the light fraction composition and reduction of the heavy vacuum gasoil and vacuum residue. Depending on the concentration, type, and active metal content of the catalysts, vacuum residue conversion in the range of 37-49% was obtained.