Functionally graded (FG) materials are now being used in versatile fields like aerospace, aviation and automobile industries, due to its high strength to weight ratio and thermal resistivity. In all of these fields the structures are often exposed to high temperature and moisture. Thus, due to the moisture absorption and increase in temperature the material properties get affected adversely, thereby leading to an abrupt change in the structural response. It is from this perspective that a forced vibration analysis is carried out on FG panels in a combined hygro-thermal environment in the present research work. The plate is assumed to be metal-rich at the bottom and ceramic-rich at the top and the variation of the material properties is based on power law model throughout the thickness. The plate is modelled considering the first order shear deformation theory and a finite element code is developed in the MATLAB platform to examine its free and forced vibrational response in a hygro-thermal environment. The geometric stiffness considering the non-linear strains is included in the present formulation to include the effect of elevated temperature and moisture concentration. A detailed numerical simulation is carried out to evaluate free and forced vibration response of different FG panels considering the temperature dependent and independent material properties and boundary conditions. The results reveal that there is a significant impact of hygro-thermal condition on structural response.