High-temperature chromium (Cr)-zirconium (Zr) interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel (ATF) claddings. Such interdiffusion changes the interfacial microstructure and thus the fracture mechanism of the coating under external loading. In this study, the interdiffusion behavior in a magnetron sputtered Cr coating deposited on a Zr-4 alloy was studied in a vacuum environment at 1160 °C. In addition, the effect of interdiffusion on the microcracking behavior of the Cr coating was determined by in situ three-point bending tests. The experimental results show that the interdiffusion behavior resulted in the formation of a ZrCr 2 layer, accompanied by the consumption of Cr coating and interfacial roughening. The growth of the diffusion layer followed a nearly parabolic law with respect to annealing time, and the residual stress of the annealed coating decreased with increasing annealing time. Under external loading, a large number of cracks were generated in the brittle interlayer, and some interfacial cracks were formed and grew at the ZrCr 2 /Zr-4 interface. Despite the remarkable microcracks in the ZrCr 2 layer, the vacuum-annealed Cr coating has significantly fewer cracks than the original coating, mainly because of the recrystallization of the coating during annealing.