The influence of experimental conditions used in the synthesis of tungsten carbide by microwave heating is described. The precursor was prepared from tungsten dissolved in hydrogen peroxide and carbon black powder. Carbon powder is consumed over the course of the synthesis; it functions as both reducing agent and carburizing agent. Carbon powder is also a microwave susceptor that is responsible for heating the reagents under microwave irradiation, and careful control of the precursor carbon content was found to be important. This paper describes the conditions required to synthesize nanoparticulate tungsten carbide to a high yield by microwave irradiation for 20 min.