In Functionally Graded Materials (FGMs) material properties vary continuously through the thickness, avoiding any material mismatch. Cracking and delamination are common problems in laminated composite materials, primarily due to material discontinuities between layers, and FGM plates overcome this drawback. The present study focuses on the static analysis of FGM plates using a general High-Order Shear Deformation Theory. The governing equations are derived using the principle of virtual displacements. The Gâteaux differential approach was employed to reformulate the governing equations to construct the mixed finite element model of the FGM plates. The behavior of FGM plates under sinusoidal and uniform loading, with simply supported and clamped boundary conditions was investigated. The results for the displacement, force, and moment components were examined based on multiple different thickness functions (f(z)). The obtained results were compared with those from different theories in the literature, and it was found that the results are consistent and accurate. © 2025 Elsevier Ltd