The kinetics of photopolymerization of thermoplastic polyurethane/acrylate blends have been studied using Real Time - Fourier Transform Infrared Spectroscopy (RT-FTIR). The polymerization rate curves were autocatalytic in nature at the initial stage of reaction; then a retardation of the reaction conversion occurred gradually as the polymer matrix became vitrified and the reaction became diffusion controlled. A kinetic rate equation with a diffusion control factor term has been employed to characterize the diffusion-controlled reaction behavior. As the reaction conversion reaches the transition point, at which the maximum value of kp/kt 0.5 in the rate expression is obtained, the reaction becomes to be controlled by diffusion due to the restricted mobility of acrylate macromonomers, resulting in the rapid drop of the polymerization rate even keeping the same reactivity of all the double bonds of acrylate macromonomers. Interpenetrating polymer networks (IPNs) of thermoplastic polyurethane/acrylate systems were formed in the limit of TPU content in the formulations. As the content of thermoplastic polyurethane increased, the polymerization rate increased in the early stage of cure reaction. Blends containing polyurethane up to 30 phr have single glass transition temperature, which indicates that they are miscible in blends and no phase separation has been observed.