The influence of the epitaxial crystallization of the polyethylene (PE) content on the adhesive interface strength of impact-toughened isotactic polypropylene (iPP) has been investigated. The morphologies and crystal arrangements of four different matrix/rubber combinations were observed by transmission electron microscopy (TEM) and were correlated with the interface strengths measured by a peel test. It was found that the adhesion is best at interfaces, where an epitaxial morphology of the PE was observed.