A method of recovering metals from a used dispersed catalyst originating from a Group VIB metal sulfide catalyst and at least a Group VB metal promoted with a Group VIII metal for hydrocarbon oil hydroprocessing, the method comprising: contacting the used dispersed catalyst with a leaching solution containing ammonia and air to dissolve the Group VIB metal and the Group VIII metal into the leaching solution at a sufficient temperature and pressure to form a pressure leach slurry containing at least a Group VIB soluble metal complex and at least a Group VIII soluble metal complex and solid residue containing at least a Group VB metal complex and coke; separating and removing the solid residue containing the Group VB metal complex and coke from the pressure leach slurry, forming a pressure leach solution; precipitating from the pressure leach solution at least a portion of the Group VIB metal and at least a portion of the Group VIII metal, wherein the precipitation being carried out at a first pre-selected pH to precipitate as metal complexes at least a portion of the Group VIB metal and at least a portion of the Group VIII metal, wherein the method further comprises: recovering the precipitated metal complexes by at least a separation means selected from settling, filtration, decantation, centrifugation and combinations thereof, forming a first supernatant substantially free of at least a portion of the Group VIB metal and at least a portion of the Group VIII metal; wherein the Group VIB metal in the used dispersed catalyst for metal recovery is molybdenum, the Group VIII metal in the used dispersed catalyst for metal recovery is nickel; and wherein the PLS is mixed with an additive selected from the group consisting of a mineral acid, a sulfur compound having a sulfhydryl group or an ionized sulfhydryl group and mixtures thereof under mixing conditions at a temperature of 50 to 95°C, a pH level of 1 to 4 and for a sufficient time for at least 90% of the molybdenum and nickel in the PLS to precipitate out as metal complexes. contacting the used dispersed catalyst with a leaching solution containing ammonia and air to dissolve the Group VIB metal and the Group VIII metal into the leaching solution at a sufficient temperature and pressure to form a pressure leach slurry containing at least a Group VIB soluble metal complex and at least a Group VIII soluble metal complex and solid residue containing at least a Group VB metal complex and coke; separating and removing the solid residue containing the Group VB metal complex and coke from the pressure leach slurry, forming a pressure leach solution; precipitating from the pressure leach solution at least a portion of the Group VIB metal and at least a portion of the Group VIII metal, wherein the precipitation being carried out at a first pre-selected pH to precipitate as metal complexes at least a portion of the Group VIB metal and at least a portion of the Group VIII metal, wherein the method further comprises: recovering the precipitated metal complexes by at least a separation means selected from settling, filtration, decantation, centrifugation and combinations thereof, forming a first supernatant substantially free of at least a portion of the Group VIB metal and at least a portion of the Group VIII metal; wherein the Group VIB metal in the used dispersed catalyst for metal recovery is molybdenum, the Group VIII metal in the used dispersed catalyst for metal recovery is nickel; and wherein the PLS is mixed with an additive selected from the group consisting of a mineral acid, a sulfur compound having a sulfhydryl group or an ionized sulfhydryl group and mixtures thereof under mixing conditions at a temperature of 50 to 95°C, a pH level of 1 to 4 and for a sufficient time for at least 90% of the molybdenum and nickel in the PLS to precipitate out as metal complexes. recovering the precipitated metal complexes by at least a separation means selected from settling, filtration, decantation, centrifugation and combinations thereof, forming a first supernatant substantially free of at least a portion of the Group VIB metal and at least a portion of the Group VIII metal; wherein the Group VIB metal in the used dispersed catalyst for metal recovery is molybdenum, the Group VIII metal in the used dispersed catalyst for metal recovery is nickel; and wherein the PLS is mixed with an additive selected from the group consisting of a mineral acid, a sulfur compound having a sulfhydryl group or an ionized sulfhydryl group and mixtures thereof under mixing conditions at a temperature of 50 to 95°C, a pH level of 1 to 4 and for a sufficient time for at least 90% of the molybdenum and nickel in the PLS to precipitate out as metal complexes.