The present work deals with the active vibration control of composite beam under thermal environment using finite element method. The effect of fiber orientation and temperature on natural frequency and damping of the system are investigated for different boundary conditions. The temperature-dependent properties of viscoelastic core are considered. Results are presented for frequencies and loss factor with different core material and core thickness. Characteristics of loss factor and frequency near the buckling temperature are discussed, and the effect of core thickness on buckling temperature is also investigated. © 2007 Elsevier Ltd. All rights reserved.