A Ni-W precursor supported on a dendrimer-containing crosslinked polymer (42 wt % of a third-generation polypropylenimine dendrimer) has been first synthesized. The precursor has been subjected to the ex situ and in situ decomposition in a hydrocarbon feedstock to prepare an unsupported Ni-W sulfide catalyst. The activity of the resulting catalyst in the hydrogenation of aromatic hydrocarbons has been studied using the example of naphthalene. The process has been conducted in an autoclave-type reactor in a temperature range of 350-400A degrees C at a hydrogen pressure of 5.0 MPa. It has been shown that the in situ synthesis of a Ni-W catalyst leads to the formation of particles exhibiting higher activity in the hydrogenation of naphthalene. The in situ synthesized Ni-W particles have been characterized by TEM and XPS.