The postbuckling failure characteristics of symmetrically laminated simply supported rectangular plates under combined uniform thermal load and uniaxial edge compression are investigated. The nonlinear postbuckling analysis is performed by the finite element method based on the first order shear deformable plate theory with the use of von Karman type nonlinear strains. The postbuckling strength is predicted by Tsai-Wu failure theory. Several numerical examples for quasi-isotropic and cross-ply laminated plates with various width-to-thickness ratios are presented. The failure space is defined by normalized axial compression and temperature change and failure envelops are obtained in the failure space. From the failure envelops obtained, it is found that the normalized axial compression and the temperature increase are in a linear relationship. It is also found that the slopes of failure envelops are almost identical regardless of the width-to-thickness ratios of plates with the same stacking sequences.