Polymeric thin films are widely used in microelectronic applications for a variety of purposes. These films may possess completely isotropic material properties and yet still exhibit anisotropic effects due to the constraining influence of the substrate coupling into the film behavior via the film Poisson ratio. A theoretical model of this effect on the through-plane thermal properties of isotropic thin films for single layer (thin film rigidly clamped) and bilayer (thin film on substrate, e.g., silicon wafer) has been developed based on the assumption that the material follows Hooke’s law in all directions. Finite element analyses using ANSYS 5.OA have also been performed to confirm theoretical results both for singlelayer and bilayer models. In the case of Poisson ratio of 0.5, the effective coefficient of thermal expansion (CTE) in the thickness direction can be as high as three times that of the unconstrained film.