To understand the molecular mechanisms responsible for the adhesion between isotactic polypropylene (iPP) and polyamide 6 (PA6) ix the presence of iPP-PA6 diblock copolymer, thin film assemblies with a typical thickness of 115 nm have been prepared. The crystalline orientation of the iPP and of the PA6 close to the interface has been investigated by X-ray diffraction. An epitaxial crystallization of iPP on PA6 was observed. Similarly to what happens for adhesive strength, the epitaxy is enhanced when increasing the copolymer surface density or the length of the PP block and further enhanced when the samples were annealed above the melting temperature of PA6.