Supported metallic catalysts comprised of a Group VIII metal, a Group VIB metal, and an organic additive, and methods for synthesizing supported metallic catalysts are provided. The catalysts are prepared by a method wherein precursors of both metals are mixed and interacted with at least one organic additive, dried, calcined, and sulfided. The catalysts are used for hydroprocessing, particularly hydrodesulfurization and hydrodenitrogenation, of hydrocarbon feedstocks.