ABSTRACTCurrent state‐of‐the‐art packaging films typically consist of solid‐state stretched multilayer polymer systems, in which each of the polymer layers provides a specific property. Often these polymer film layers are incompatible and need to be glued together by so‐called “tie layers.” In this article, we apply a novel biaxial orientation technique to examine the effect of solid‐state biaxial stretching on the adhesive behavior of a model multilayer system consisting of poly(ethylene terephthalate) and isotactic polypropylene, as an example of two typical incompatible base layers, glued together by a common tie layer. Two main factors affecting the adhesion, the temperature at which the biaxial stretching is performed and the thickness of the tie layer, are discussed in detail. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 446–454