This study numerically investigates the effect of material gradation on the nonlinear mechanical performance and load-carrying capacity of reinforced concrete (RC) beams externally strengthened with functionally graded material plates (FGMPs) bonded to the tension face. Using the ANSYS finite element platform, the research aims to quantify how varying gradation indices influence key structural performance metrics, including ultimate load capacity, mid-span deflection, stress and stress distribution across the beam–plate interface, and crack propagation behavior. The nonlinear constitutive behavior of concrete is modeled as quasi-brittle, while the FGMP is represented using a bilinear elastoplastic model. The smooth throughthickness variation of elastic and plastic properties within the FGM plate is defined using both the nonlinear power gradation law and the Tamura–Tomota–Ozawa (TTO) models. In the finite element framework, the RC beam and FGM plate are discretized using 3D solid elements (SOLID 65 for concrete and SOLID 185 for the plate), whereas the steel reinforcement is modeled using LINK180 elements. The interaction between the concrete substrate and the FGMP is captured using a layered solid shell formulation (SOLSH 190) to simulate interfacial behavior accurately. Both static performance and failure modes are evaluated under incremental loading conditions. The validity of the proposed FE model is established through comparison with existing literature, demonstrating strong agreement between the results. The effects of functionally graded material distributions, gradation index, and plate thickness on load capacity, maximum deflection, induced interfacial stresses, and crack patterns are examined and analyzed. The findings reveal that FGMPs with higher ceramic content significantly enhance the beam’s stiffness, ultimate load capacity, and resistance to cracking. The outcomes of this study contribute to the development of reliable computational tools for designing FGM strengthened RC structures subjected to complex mechanical loading