The thermal buckling analysis of functionally graded (FG) arbitrary straight-sided quadrilateral plates is presented. The material properties are assumed to be temperature-dependent and graded in the thickness direction. The thermal buckling equilibrium equations are based on the three-dimensional (3D) elasticity theory. The differential quadrature method as an efficient and accurate numerical tool is adopted to discretize the governing equations. The principle of virtual work in conjunction with the geometric mapping technique is used to derive the equilibrium equations and the related boundary conditions. After discretizing the governing equations, the resulting nonlinear eigenvalue system of equations is solved by an iterative procedure. The convergence of the method is shown through different examples and its accuracy is demonstrated by comparing the obtained solutions with the existing results in literature for FG plates. Finally, the effects of temperature dependence of material properties, temperature field, volume fraction index, geometrical parameters and the boundary conditions on the thermal buckling characteristic of the FG plates of various shapes are studied.