The use of fiber-reinforced polymer (FRP) plates for the strengthening of structural members involves their exposure to service temperature variations (i.e., thermal loadings). Such temperature variations may lead to thermal stress and the interfacial debonding of the FRP-plated beam as a result of the thermal mismatch between the FRP plate and the substrate beam. There is lacking research related to the effect of temperature variations on the interfacial debonding of FRP-plated beams. This paper presents the first-ever analytical study on the behavior of the FRP-plated beam under combined thermal and mechanical loadings. The interfacial stress and slip evolutions as well as the debonding process of the FRP-plated beam are estimated based on a coupled mix-mode cohesive zone modeling. In addition, a finite element (FE) approach is proposed to verify the analytical solution in which the analytical results are compared with the FE model predictions, indicating that a good agreement was achieved between the analytical and FE results.