Blends of high-density polyethylene (HDPE) and isotactic polypropylene (iPP) are used to increase the strength of adhesive bonds between the immiscible polymers HDPE and iPP. Melt blended as well as solution blended material is examined for its suitability to compatibilize the interface between the bonded members. Two standard test methods, the T-peel test and the tensile test, are applied to determine the strengths of adhesive joints. Laminated samples for the peel-tests as well as specimens subjected to the tensile tests were prepared at a temperature exceeding the melting temperature of both homopolymers. TEM and LVSEM examinations were performed for characterizing the morphology of the interface with the aim to determine the parameters which significantly influence the blends' adhesive properties. The bonding strengths obtained with the blended material are discussed with respect to the morphologies of the interfaces, the degree of dispersion in the blend, and the bonding mechanisms.