Few studies deal with the properties of niobium sulfide as a hydrodesulfurization catalyst. In this paper, the preparation of carbon-supported niobium sulfide catalysts was optimized concerning (ii) the nature of the soluble precursor, (ii) the drying process, and (iii) the sulfurizing treatment, which was always performed under atmospheric pressure but for different H2S-based hows and reaction temperatures. The activities of the best samples prepared with niobium oxalate as the impregnation salt, drying at room temperature, and presulfurization with N-2/H2S at 400 degrees C are superior to that of a supported MoS2 reference catalyst. Alumina-supported systems can be sulfurized only under more severe conditions (CS2 under pressure). After optimization of the sulfurization treatment (400 degrees C, 10 h) the maximum activity obtained is significantly higher than that of a molybdenum sulfide reference catalyst. The catalytic activities of the various catalysts studied are related to their morphological and chemical characteristics using TPR and EXAFS measurements. The work illustrates the importance of the support and the sulfurization method on the genesis of a niobium sulfide active phase.