The invention relates to a self-supported mixed metal sulfide (MMS) catalyst for hydrotreating hydrocarbon feedstock and to a method for preparing the catalyst. The MMS catalyst is characterized as having a BET surface area of at least 20 m2/g and a pore volume of at least 0.05 cm3/g. In one embodiment, the MMS catalyst is also characterized as having a multi-phased structure comprising five phases: a molybdenum sulfide phase, a tungsten sulfide phase, a molybdenum tungsten sulfide phase, an active nickel phase, and a nickel sulfide phase.