The effect of phosphorus on Mo2C supported on gamma-Al2O3 and activated carbon was studied. The catalysts were characterized by CO chemisorption, BET surface area measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure, and tested for their reactivity for hydroprocessing reactions, particularly hydrogenation, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN), using model liquid compounds. The P-containing catalysts had higher reactivity for HDN than those without P. HDS was higher when the Mo2C was synthesized on gamma-Al2O3 previously treated with P than when the Mo component and P were added together on gamma-Al2O3. Postreaction characterization indicates that the catalysts were tolerant of sulfur.