The time dependence of a reinforcement-matrix interfacial layer growth (RMILG) in most metal matrix composites (MMC＇s) is not t(1/2) as described by Fick＇s law. Moreover, the RMILG vs. t(1/2) could be linear for relatively short and long times, and an anomaloustransition behavior exhibits in between. In this paper, a dual-phase-lag diffusion (DPLD) model is proposed to characterize the RMILG kinetics. Unlike Fick＇s law, it accounts for the two lagging times required for the processes of interdiffusion and chemical reaction. This unique feature empowers the DPLD model to capture the multiple stages response over the entire RMILG history. Model validation is verified with the experimental results of seven different MMC systems.