Unsupported Ni-Mo and Ni-W sulfide catalysts for the hydrogenation of polymeric petroleum resins are ex situ in a hydrocarbon solvent by the decomposition of oil-soluble bimetallic precursors. It is shown that the activity of the nanocatalysts is higher than that of conventional supported catalysts. The Mo: Ni ratio (1.5: 1) provides the maximum conversion of aromatic and unsaturated moieties of the substrate molecule. It is found that an increase in the process temperature and pressure leads to intensification of polymer chain degradation reactions. The highest degree of hydrogenation is achieved in polymeric petroleum resin solutions with a concentration of 40 wt %; further increase in concentration contributes to the inhibition of thermal degradation reactions. It is shown that the catalyst can be reused without any loss of activity; in addition, the degree of sulfiding of the active phase remains unchanged and the particles do not undergo agglomeration.