The present paper intends to probe the modal behaviour of beam like structures made of functionally graded material under thermal stresses. In various engineering sectors such as spacecraft, aircraft and thermal power plants, it is noticeable that at times, structures operate under severe thermal environment experience vibrations. Thereby, to accurately predict such vibrations in order to provide the mitigating action, various condition monitoring methods are adopted. However, in all such condition monitoring techniques, the modal characteristics of the structure play a crucial role. The modal behaviour of structures at elevated temperature is quite different from the normal conditions due to the induced thermal stresses. The pre-stressing due to thermal effects causes stiffening or de-stiffening in the structures altering their modal properties significantly. Therefore, in the present work, the natural frequency of beam structures made of functionally graded material is calculated under different temperatures and boundary conditions. In addition to that, the effect of alteration of material layer of functionally graded material on natural frequency and stress distribution is further being simulated. The simulation is performed using the finite element analysis in ABAQUS/CAE. The accuracy of the simulated results is insured by comparing some of the results with the available results in open literature. Finally, a parametric study is performed to report the combined effect of on the temperature, boundary conditions and gradation relations on the modal properties of FGM plates.