In order to investigate the effect of CdCl2 heat treatment on the physical properties of CdTe thin films grown by a sputtering method, the CdTe thin films were coated with CdCl2. The recrystallization, grain growth, randomization, and reaction kinetics were investigated by monitoring the phase transition of CdCl2-heat-treated CdTe specimens during temperature ramp annealing or isothermal soaking by using in-situ time-resolved high-temperature X-ray diffraction. The results of annealing show that the recrystallizations of CdTe (1 1 1) and other planes do not occur simultaneously, but sequentially in terms of temperature. The results of isothermal soaking imply that the Avrami diffusion-controlled reaction model fits well with the experimental data. This proves that the CdCl2 diffusion process is the dominant factor in the CdTe recrystallization mechanism. (C) 2011 Elsevier B.V. All rights reserved.