The synthesis and characterization of magnesium ferrite MgFe2O4 prepared by co-precipitation and sol gel combustion is reported. Structural characterization showed that all the samples have single spine! phase. The co precipitated sample exhibits smaller grains and twice higher BET surface than the sol gel combustion samples. The powder was shaped to dedicated chemo-resistive home-made sensors devices. The electrical properties and sensing properties towards carbon dioxide of both MgFe2O4 powders were studied. The type of cWar& crrieff were analysed on the basis of the change in resistance in the presence of air and argon. The sensing response towards CO2 was found to be dependent on the morphology of the powder sample and the CO2 concentration. A high response of 36% towards 5000 ppm of CO2 was reached which is good for this gas. The key role of the Mg ions modulating the electrical properties is discussed.