Polymer adhesion and its evaluation are very important both from academic and industrial points of view. Adhesion phenomenon depends mainly on the strength of interfacial bonds and the deformability of adhering partners, which act as another energy absorbing term. Using a combination of acid-base interactions and a coupling agent at the interface of styrene-butadiene (SBR)-polyurethane system, a synergistic adhesion promotion was observed. The SBR surface was treated with an acidified aqueous solution of calcium hypochlorite to obtain polar groups, which can interact with the isocyanate groups of the polyurethane system. Aminopropyltriethoxysilane, a coupling agent, was also deposited at the SBR surface, after treating it with the aforementioned solution. The polar groups on the SBR apparently interact with the OH sites of the coupling agent at the surface and push the amino groups toward the polyurethane surface. This interesting finding, synergistic adhesion promotion, was attributed to the tortuous path for the crack growth at the interface, which was created by formation of the interfacial bonds with different strengths (heterogeneous bond strength). Furthermore, to obtain the highest synergistic effect, it seems that certain ratio of bonds with different strengths should be formed. The ratio itself depends on the deformability ratio of the adhering materials.