Mixed sulfide Nb2Mo3S10 was obtained by reaction of H2S with the mixed oxide Nb2Mo3O14 at 873 K. High-resolution electron microscopy and X-ray diffraction show the formation of homogeneous lamellar mixed sulfide. Due to the increased lability of oxygen, the sulfidation of the mixed oxide is easier compared to that of Nb2O5 oxide. As follows from the characterization of transient solid products, the transformation from the oxide to the sulfide includes the intermediate formation of a partially reduced "bronze" compound. For the thiophene hydrodesulfurization model reaction, the catalytic properties of Nb2Mo3S10 mixed sulfide are intermediate between those of the individual MS2 sulfides (M=Mo, Nb), but closer to those of the Nb compound.