In this article, the free vibration behavior of functionally graded carbon nanotube reinforced composite plate is investigated under elevated thermal environment. The carbon nanotube reinforced composite plate has been modeled mathematically using higher order shear deformation theory. The material properties of carbon nanotube reinforced composite plate are assumed to be temperature dependent and graded in the thickness direction using different grading rules. The effective material properties of the functionally graded plate are introduced in the present model through a micromechanical model under temperature load. The governing differential equation of the functionally graded carbon nanotube reinforced composite plate is obtained using Hamilton’s principle. The domain is discretized using the suitable isoparametric finite element steps and solved numerically through a computer code developed in MATLAB environment. The validity and the convergence behavior of the present numerical results have been checked and a simulation model is also developed in commercial finite element package (ANSYS) using ANSYS parametric design language code. The effect of various geometrical parameters (aspect ratios, support conditions, and thickness ratios), the grading effect, and the temperature variation on the free vibration behavior of functionally graded carbon nanotube reinforced composite are examined and discussed in detail.