Magnesium silicide based alloys fast syntheses have been carried out using microwave heating. Precursors were first ball milled powders together under inert gas. Resulting powders were then placed into a glassy carbon crucible before being heated by microwave irradiation. Sintering of the powder was performed by spark plasma method. XRD and SEM/EDS were used to investigate composition, structure and morphology. Thermoelectric performances of the samples were measured in the temperature range of 320–775K. The doping effect of several elements such as silver, tin, antimony, cobalt and bismuth has been studied. n-Type and p-type Mg₂Si based materials have been successfully synthesized, with maximum ZT value up to 0.7 and 0.35 at 770K for a n-type and a p-type sample, respectively. We demonstrate here that the use of microwave irradiation to prepare doped Mg₂Si is possible, and we discuss here the thermoelectric properties of such samples.