Hierarchical tungsten carbide (WC) micro-/nanocrystals were synthesized by thermal treating a single-source precursor of the tungstate-based inorganic-organic hybrid compound in a sealed quartz tube at 1000 degrees-1050 degrees C. The hybrid precursor was synthesized by an acid-base reaction of H(2)O-moistened H(2)WO(4) and n-octylamine in a nonpolar solvent. The X-ray diffraction results indicated that the product obtained at 1050 degrees C for 2 h consisted of a hexagonal WC phase, and the products obtained at temperatures lower than 1000 degrees C had other phases (e.g., alpha-W(2)C, W or beta-W(40.9)N(9.1)) besides the major phase of hexagonal WC. The scanning electron microscopy observations indicated that the hexagonal WC obtained at 1050 degrees C consisted of hierarchical microparticles with a size range of 4-18 mu m, and the above microparticles were porous aggregates of WC nanoparticles with crystal sizes of 100-250 nm. The newly developed process could achieve pure WC materials at relative low temperatures using a single-source precursor, and the porous and hierarchical WC micro-/nanoparticles would have potential applications in catalysis and superhard composites.