This paper describes a dynamic heterogeneous one-dimensional model of trickle-bed reactors used for catalytic hydrotreating of oil fractions. The model considers the main reactions in the hydrotreating process of oil fractions: hydrodesulfurization, hydrodenitrogenation, and hydrodearomatization. The dynamic model was first validated using experimental data obtained in an isothermal pilot reactor during hydrotreating of vacuum gas oil over a commercial NiMo catalyst. Then, the model was applied to predict the dynamic behavior of a commercial hydrotreating reactor. Changes in concentration, partial pressure, and temperature profiles are obtained and discussed as a function of reactor axial position and time. The simulations obtained with the proposed dynamic model showed good agreement with experimental data.