Abstract The phase diagram of Sr–Co–O system was assessed based on the analysis of thermodynamic behavior of solid samples in air atmosphere. Samples of several compositions were prepared by standard ceramic route consisting of solid state reaction and sintering for long time periods followed by slow cooling to ensure the formation of thermodynamically stable phases. The equilibrated samples were then analyzed by DTA/TG and high temperature phase relations were studied by numbers of quenching experiments. The thermodynamic data of the involved phases were assessed based on the experimental results and the phase diagram for air atmosphere was calculated using the FactSage program.