The interdiffusion reactions between Zircaloy-2 and a Ni based alloy (Inconel 750X) have been studied in the temperature range 1083–1173 K by employing annealing of diffusion couples. The reaction zone developed at the interface was characterised using an optical microscope and electron probe microanalyser (EPMA). The diffusion reaction between Zircaloy-2 and Inconel shows that the reaction products form both as a layered structure and as two phase mixture in the diffusion zone. Three layers were found to form in the diffusion zone, namely, Zr₂Ni (x phase) and Y₁ phase close to Zircaloy-2 and a mixture of Y₁ and Y₂ phases close to Inconel. The kinetics for the growth of the three layers as well as the total diffusion zone was established. The growth of all the layers shows Arrhenius type of relation with respect to temperature. The temperature dependence for the reaction constants, K, for the various phases was also established.