Abstract The elements of high-frequency circuits, such as waveguide filters, are often subject to high temperatures due to power losses. Thermal expansion of the materials comprising the filter causes its deformation, which can significantly modify the S-parameters of the filter. In this work, the influence of thermal expansion on the properties of a waveguide filter is investigated. At first, the filter is heated up by about 100K. Then, a linear structural mechanics solver estimates the distribution of displacements within the system due to thermal expansion of its materials. Finally, sensitivity analysis with respect to this distribution of node displacements is performed. The results of sensitivity analysis are validated by their comparison with those obtained for a similar manual deformation of the system geometry. It is shown that the resulting scattering parameters are very similar in both cases, which confirms the reliability of the method. Moreover, the presented method does not require additional simulations for sensitivity estimation, which allows the analysis to be performed with no computational overhead.