Adhesion in immiscible, weakly bonded polymeric layered structures is explored. Of particular interest are common commercial polymers used in multilayered packaging materials. Based on the scission of entangled chains at the polymer-polymer interface, a correlation between the critical mechanical energy release rate for fracture (Gc) and the characteristic number of interfacial entanglements (Nent) is developed. Nent, the ratio of the interfacial width to the average length scale required for entanglement, is calculable for a variety of homopolymers and random copolymers. Results of adhesion tests on melt and solvent laminated samples, coupled with random copolymer data from the literature, verify that a Gc ∝ Nent2 relationship exists. For small Nent, there are insufficient entangled chains to strengthen the interface, and the critical mechanical energy release rate goes to zero. The proposed model offers a method for designing new materials from common immiscible polymer systems.