The effect of glycols on the catalytic properties of phosphate-doped NiMo/Al 2 O 3 catalysts in the hydrotreating of straight-run gas oil (SRGO) was studied. The NiMo(P)/Al 2 O 3 catalysts were prepared using ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) as additives. The organic agent was introduced into the aqueous impregnation solution obtained by the dissolving of MoO 3 in H 3 PO 4 solution, followed by Ni(OH) 2 addition. The Raman and UV–Vis studies show that the impregnation solution contains diphosphopentamolybdate H x P 2 Mo 5 O 23 (6−x)− and Ni(H 2 O) 6 2+ , and that these ions are not affected by the presence of glycols. When the impregnation solution comes in contact with the γ-Al 2 O 3 surface, H x P 2 Mo 5 O 23 (6−x)− is decomposed completely. The catalysts were characterized by Raman spectroscopy, low-temperature N 2 adsorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is shown that the sulfide catalysts prepared with glycols display higher activity in the hydrotreating of straight-run gas oil than the NiMoP/Al 2 O 3 catalyst prepared without the additive. The hydrodesulfurization and hydrodenitrogenation activities depend on the glycol type and are decreased in the following order: NiMoP-DEG/Al 2 O 3 > NiMoP-EG/Al 2 O 3 > NiMoP-TEG/Al 2 O 3 > NiMoP/Al 2 O 3 . The higher activity of NiMoP-DEG/Al 2 O 3 can be explained with the higher dispersion of molybdenum on the surface of the catalyst in the sulfide state.