A kinetic model is developed to simulate the thermal decomposition of dicumyl peroxide (DCP) in cumene with and without oxygen in the reacting system, based on a reaction network that is comprised of a set of 51 reactions. An optimization procedure is adopted to obtain the best estimates for most of the related kinetic parameters, few of which are available in the literature. The model is successfully validated by simulating the concentration profiles of all the species participating in the decomposition of DCP in cumene, under varying initial conditions, using previously best-estimated values of the kinetic parameters.