Large pore, high surface area mesoporous zirconia was synthesized using P123 as structure directing agent and was used as support material for hydrotreating of heavy gas oil. The mesoporous zirconia supported NiMo hydrotreating catalyst was prepared with and without EDTA via incipient wetness impregnation method. The structural characteristics of catalysts were measured by X-ray diffraction (XRD), FT-IR, RAMAN, TPD (Temperature Programmed Desorption), TPR (Temperature Programmed Reduction), HRTEM, XANES and N-2-adsorption desorption isotherms (BET). The hydrotreating activities of the catalysts were measured using Athabasca bitumen derived heavy gas oil at industrial reaction conditions. Catalytic activity of NiMo/gamma-Al2O3 and NiMo SBA-15 catalysts was also determined for comparative studies. Low angle XRD and BET results support the formation of ordered mesoporous structure in the catalyst. Wide angle XRD, FT-IR and RAMAN analyses confirm the presence of mixture of monoclinic and tetragonal phase of zirconia in the catalyst. Surface acidity and type of acidic sites present were measured using NH3-TPD and Pyridine-FTIR. The extent of active metal dispersion in NiMo/Meso-Zr, Ni(NO3)(2)-Mo/Meso-Zr and NiMo/Meso-Zr(EDTA) catalyst is shown by CO chemisorption and HRTEM analysis. It has been confirmed from physio-chemical characterization that addition of EDTA increases the catalytic activity by (i) increasing the active metal dispersion as indicated by HRTEM and CO chemisorption, (ii) increase in Ni sulfidation temperatures and (iii) decreasing the metal support interaction as shown by XANES analysis. XANES analysis revealed that molybdenum oxide is present predominantly in tetrahedral form in NiMo/Meso-Zr catalyst whereas its present predominantly in octahedral form in NiMo/Meso-Zr (EDTA) catalyst. The catalytic activity was investigated and corelated systematically with the textural and structural properties of the catalysts.