Abstract: To extend Reddy’s theory to accurately analyze the thermal deformations and stresses of laminated composite and sandwich structures, an enhanced Reddy’s theory for laminated composite beams was proposed by using the transverse normal thermal deformation in transverse displacement as well as the free surface conditions. Although transverse normal strain is involved, the number of unknowns in the proposed model is the same as that in Reddy’s theory. Using the principle of virtual work, the equations of equilibrium for laminated composite beams were presented, and the thermal expansion problems of laminated composite and sandwich beams were analyzed. Numerical results show that the enhanced Reddy’s theory can accurately analyze the thermal expansion problems of laminated composite and sandwich structures. However, Reddy’s theory is less accurate for thermal expansion problems.