This work describes a novel synthesis for the production of very pure nanocrystalline hexagonal nickel sulfide phase (h-NiS) by the solventless route in air at temperatures of only 190 °C. Only the cubic NiS 2 nickel sulfide phase is obtained when the sulfur source reacting with the nickel acetate powder (NiAc) is switched from thiourea (TU) to elemental sulfur (S N). When using both TU and S N sulfur sources, phase mixture of h-NiS, NiS 2 and Ni 3 S 4 with less aggregated particles was obtained. Relative concentrations of the phases were quantified by the Rietveld refinement of the XRD powder patterns. The thermal evolution of stoichiometric reagents mixture was observed by TG-FTIR and DSC curves.