In this work, a-systematic study has been conducted to optimize the process conditions and to evaluate kinetic parameters for hydrodenitrogenation (HDN) and hydrodesulphurization (HDS) of heavy gas oil derived from Athabasca bitumen using NiMo/Al2O3 catalysts containing phosphorus (P). In the catalyst, the concentration of phosphorus was maintained at 2.7 wt%. Experiments were performed in a tickle-bed reactor at the temperature, pressure and liquid hourly space velocity (LHSV) of 340-420 degrees C, 6.1-10.2 MPa and 0.5-2 h(-1), respectively. H-2 flow rate and catalyst weight were maintained constant at 50 mL/min and 4 g, respectively in all cases. Statistical analysis of all experimental data was carried out using ANOVA to optimize the process conditions for HDN and HDS reactions. Kinetic studies for HDN and HDS reactions were studied within the temperature range of 340-400 degrees C using the power law model as well as the Langmuir-Hinshelhood model. The power law model showed that HDN and HDS of heavy gas oil follow first order kinetics. The activation energies for HDN and HDS reactions from the power law and Langmuir-Hinshelwood models were 94 and 96 kj/mol and 113 and 137 kj/mol, respectively.