Induction hardening is a non contact heating process which utilizes the principle of electromagnetic induction to generate heat on the surface layer of a work-piece. By placing a conductive material into a strong alternating magnetic field, electrical current flows in thin surface layer, following the ‘skin-effect’ in the metallic material by electromagnetic induction (eddy current), generating heat at the surface due to the I2R losses in the material. When the current flows in the surface layers it heats up the component starting from the surface by the I2R heat maximizing at the depth of penetration. In magnetic materials, further heat is generated below the Curie temperature due to hysteresis losses. The effect of induction case hardening of a gray cast iron (FG 260) and SG iron (600/3) as a function of applied induction power has been studied. The influence of various operating parameters on the penetration depth has been analysed. The case depth as a function of applied power and the associated changes in microstructure has been investigated. The case depth of SG iron was found to be twice than the gray iron due to higher resistivity of the material and increase in depth of penetration. Both hardness and the depth of penetration increased with increase in applied power associated with martensitic case formation. The surface hardness of both the irons varies between 600 to 800 VHN. The core microstructure in both the irons displayed pearlitic matrix. In the case of SG iron, the nodule size, sphericity and nodularity have reduced in the induction hardened case compared to the core.