During the oxychlorination of ethylene, the composition of the catalyst, cupric chloride, is subject to change, and hence estimation of rate parameters considering the unsteady-state situation is more reliable than assuming steady state. In the present work, nonisothermal experimental data are collected in an unsteady-state fixed-bed reactor by changing the inlet temperature using a temperature-programmed preheater. The rate parameters are estimated by developing an unsteady-state model which takes into account not only the reaction temperature and gas-phase conversions but also changes in the solid-phase composition in the catalyst bed. The rate parameters estimated in this study are found to be different from the steady-state values reported in the literature. The disagreement in the rate parameters has been explained in terms of the properties associated with the solid phase. The most significant feature of this work is that the rate-temperature behavior, calculated using the present rate constants, corresponds closely with that derived from independent catalyst composition studies reported in the literature, thus indirectly validating the parameters estimated in this work.