The aims of this research is to experimentally investigate the post-wrinkling behavior in GFRP cell-core sandwiches with orthotropic webs as well as the applicability of existing theories, e.g. the rotated stress field theory, to orthotropic FRP material systems. Through biaxial compression-tension experiments on web-core panels, the redistribution of the strain field during post-wrinkling was examined for two different fiber architectures, [90/0] and [±45] stacking sequences. The results prove that the fiber architecture greatly influences the wrinkling loads, the wrinkling mode as well as the post-wrinkling behavior. Furthermore, the results show that taking into account the post-wrinkling behavior can increase the ultimate strength of the whole sandwich structure and/or add redundancy to the system which enhances the safety, functionality and reliability level of the structure.