A detailed study has been made of interdiffusion in ZnSe‐ZnTe strained‐layer superlattices (SLSs) grown by molecular‐beam epitaxy (MBE) at a growth temperature of 320 °C. In x‐ray diffraction measurements, the satellite peak intensities relative to the zero‐order peak intensity decreased with annealing time. The interdiffusion coefficientDwas calculated assuming a linear diffusion model. The values ofD=3.6×10−21to 2.2×10−19cm2/s at an annealing temperature of 500 °C were obtained for the ZnSe‐ZnTe SLSs. In the high‐resolution transmission electron microscopy (HRTEM) image of as‐grown SLSs, the presence of fine superlattice structures was seen, but for interdiffused samples stripes due to the periodic superlattice structures were not visible and many dislocation lines were observed. These results suggest that the structure of SLSs is significantly modulated by thermal annealing at a temperature higher than the growth temperature.