Nanocrystallite ferrites samples with general formula Mg1-xCdx Fe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by oxalate co-precipitation method from high purity sulphates. The samples were characterized by XRD, SEM and FT-IR techniques. The phase identification of powder reveals single phase cubic spinel nature of materials. The gas sensing properties were studied for ethanol (C2H5OH), liquid petroleum gas (LPG) and chlorine (Cl2). The MgFe2O4 is sensitive to LPG (~ 80%) followed by Cl2 (~75%) and less to ethanol (~ 58%) at an operating temperature of 225oC. The sample with x = 0.4 has highest sensitivity at operating temperature 225oC for LPG (~ 78%). It shows good sensitivity at operating temperature at 198oC for Cl2 (~75%) and ethanol (~ 65%). The CdFe2O4 sensor (x=1) exhibits very high sensitivity (85%) and good selectivity to ethanol than other tested gases such as LPG (~ 35%) and Cl2 (~ 30%). The response and recovery time decreases with increase in Cd2+ content for LPG, Cl2 and ethanol. The shorter response is observed to CdFe2O4 for LPG, Cl2 and ethanol.