In this paper, the free vibration behaviors of the functionally graded (FG) coated and undercoated plates are studied by a meshfree boundary-domain integral equation method. Based on the twodimensional elasticity theory, the boundary-domain integral equations for each single layer of these coating-substrate plates are derived initially by using elastostatic fundamental solutions. Employ the radial integration method to transform the domain integrals into boundary integrals and achieve a meshfree scheme. By applying the multi-region boundary element method, obtain the generalized eigenvalue system of the whole plate, which involves system matrices with boundary integrals only and the complete solutions for natural frequency and vibration modes are rigidly resolved. A comparative study of FG versus homogeneous coating is conducted. The influences of material composition, material gradient, coating thickness ratio, plate aspect ratio and the boundary conditions on the natural frequencies of the FG coated and undercoated plates are evaluated and discussed.