Nanosized WC-Co composite powders were produced by a chemical vapor synthesis (CVS) process. The reactions of vaporized chlorides (WCl6 and CoCl2) With methane-hydrogen mixtures produced nanosized WC-Co composite powder, which sometimes contained WC or W phase. The effects of reactant concentrations, WCl6 volatilizer temperature, and H-2 to CH4 molar ratio in the feed stream were investigated. The produced powder was heat-treated under hydrogen to fully carburize all tungsten carbide phases to WC and reduce carbon content down to nearly stoichiometric levels. Finally, WC-Co composite powders of particle size less than 70 nm with 0-3% excess carbon were obtained.