Functionally Graded Materials (FGM) are used as thermal barrier materials or heat shielding properties in modern applications fields like aerospace, aeronautic, and fusion reactors. Intensive studies have focused on the thermal buckling of FG sandwich plates to investigate their local instability. This study provides a nonlinear solution for the thermal buckling of doubly supported FG sandwich plates, based in a refined exponential shear deformation plate theory (RESDPT). The FG sandwich plate under consideration is composed of a metal-ceramic mixture. The metallic element is a Grade 5 Titanium alloy (Ti-6Al-4V: containing 6% Aluminum as well as 4% Vanadium) and the ceramic element is Zirconia (ZrO2: Zirconium Oxide). Rectangular symmetrical and non-symmetrical types of sandwich plates are studied, the FGM surface sheets have been aligned with a homogeneous core, the FGM would be in the core, and the surface sheets are in the form of a homogeneous material. The Navier’s approach has been used to solve the system of equilibrium equations. Three types of thermal loading vary across the thickness direction are used: uniform thermal loading, linear, and nonlinear. To demonstrate the accuracy of the present solution, a comparison of the solution to different theories in literature and a discussion on the influence of geometric parameters on the critical buckling value are provided.