Graphene nanoplatelets (GPLs) are considered to be a desirable reinforcing nanofillers for nanocomposite materials owing to their superior thermo‐mechanical properties. Meanwhile, thermoelastic damping (TED), as a dominant intrinsic dissipation mechanisms, is a major challenge in optimizing high‐performance micro/nano‐resonators. Nevertheless, the classical TED models fail at the micro/nano‐scale due to without considering the influences of the size‐dependent effect and the thermal lagging effect. The present work focuses on investigating TED analysis of functionally graded (FG) microplate resonators reinforced with GPLs based on the modified coupled stress theory (MCST) and the Moore–Gibson–Thompson (MGT) heat conduction model. Four patterns of GPLs distribution including the UD, FG‐O, FG‐X and FG‐A pattern distributions are taken into account and the effective mechanical properties of the plate‐type nanocomposite are evaluated based on the Halpin–Tsai model. The energy equation and the transverse motion equation in the Kirchhoff microplate model are formulated, and then, the closed‐from analytical solution of TED is solved by complex frequency method. The influences of the various parameters involving the material length‐scale parameter, the thermal phase lag of the heat flux and the total weight fraction of GPLs on the TED are discussed in detail. The obtained results show that the effects of the modified parameter on the TED are pronounced. This results provide a more reasonable theoretical approach to estimate TED in the design of FG microplate resonators reinforced with GPLs with high performance.