A bimetallic nickel–molybdenum catalyst supported on γ -alumina was synthesized by the two-step incipient wetness impregnation technique. The activity of the prepared Ni–Mo/ γ -alumina catalyst was evaluated in a down flow fixed-bed micro-reactor. In this way, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions of the main distillate fractions of crude oil were assessed. XRD, SEM, TPR, ICP-OES, BET–BJH and nitrogen adsorption/desorption methods were used for characterizing the synthesized Ni–Mo/ γ -alumina catalyst. The active metals with Ni/Mo mass ratio of 0.23 and total metal of 13.7 wt% were loaded on the support, similar to the commercial industrial catalyst. The performance tests were conducted at 3.0 MPa (for light naphtha and heavy naphtha) and at 4.5 MPa (for kerosene and gas oil). The results revealed that the total sulfur conversion of the light naphtha, heavy naphtha, kerosene and gas oil fractions was 98.3%, 95%, 91.7% and 90.1% (after 24 h), respectively.