Nanostructured Co-Al coating on Superni-718 substrate was deposited by dc/rf magnetron sputtering. The high temperature oxidation kinetics of Co-Al coating on superalloy substrate was studied after 100 h of cyclic oxidation in air environment at 700-900°C. FE-SEM/EDS, AFM and XRD were used to characterise the microstructure, surface morphology and phase constituents of as deposited and oxidised coatings. The results indicate that the Co-Al coated superalloy substrate has higher oxidation resistance at 900°C. The presence of β-CoAl intermetallic phase in the Co-Al coating, the formation of Al 2O 3 and spinel phases such as CoCr 2O 4 and CoAl 2O 4 in the oxide scale are considered to be the reasons for the higher oxidation resistance shown by the Co-Al coated superalloy substrate after 100 h of cyclic oxidation in air at 900°C. Further, the oxide scale formed on the coated sample exhibits good spallation resistance during cyclic oxidation test at 900°C. © 2012 Institute of Materials, Minerals and Mining.