The measurement of thermal stress of SrF2films on InP as a function of temperature is presented. Theinsituandexsiturapid isothermal annealed films have different values of thermal stress at room temperature and show entirely different behavior of thermal stress during heating and cooling cycles. X‐ray photoelectron spectroscopy measurements were used to characterize the surface of the SrF2films as well as the SrF2/InP interface for both theexsituandinsituannealed films. It is shown that the difference in the microstructure ofinsituandexsiturapid isothermal annealed SrF2films on InP is indeed reflected in the significant difference in the thermal stress.