The effects of compatibilizer and the number of layers on the interfacial adhesion and delamination model of coextruded microlayer samples consisting of alternating layers of high-density polyethylene (HDPE) and polyamide 6 (PA6) were studied with T-peel test. When more maleic anhydride-grafted HDPE was incorporated into HOPE layer, the interfacial delamination model changed from adhesive to cohesive failure in the case of bilayer samples. For high-layer samples, the results of X-ray photoelectron spectroscopy showed that the areal density of copolymers at the interfaces increased with increasing number of layers due to strong and durable shearing forces during microlayer coextrusion. Scanning electron microscopy observation revealed that the interfacial delamination model changed from single-to multiple-interface delamination when the number of layers increased from 16 to 32. The crack propagation included a large number of layer-layer jumps. The peel strength of microlayer samples was found to be greatly influenced by the interfacial delamination mechanisms. POLYM. ENG. SCI., 50:1111-1121, 2010. (C) 2009 Society of Plastics Engineers