Methods for hydroprocessing of hydrocarbon feedstocks, including hydrodesulfurization and hydrodenitrogenation, using rejuvenated supported metallic catalysts are provided. The supported metallic catalysts comprised of a Group VIII metal, a Group VIB metal, are rejuvenated by a process making use of these metals, an organic complexing agent, and optionally an organic additive. The rejuvenation includes stripping and regeneration of a spent or partially spent catalyst, followed by impregnation with metals and at least one organic compound. The impregnated, regenerated catalysts are dried, calcined, and sulfided.