According to Gibbs, the free mixing energy is decisive for the thermodynamic compatibility of two substances. If the free mixing energy is positive, the two mixing partners are separated. For such molecularly immiscible polymers, a finely distributed disperse phase within the matrix can only occur if a drop breaks open during processing as a function of the strain and shear rates. If all preconditions are met, coupling agents can be used to improve the phase adhesion of both polymers and to stabilize the morphology. This is due the reduction of the interfacial tension, thus facilitating drop breakage and simultaneously increasing interfacial tension, which suppresses coalescence. In this work the effect of three different coupling agents (maleic anhydride, itaconic acid and glycidyl methacrylate) is investigated to evaluate their influences on the property changes in polyamide 6/ethylene-octene-copolymers-blends. All blends have a fixed mixing ratio of 80/20 and were produced on a twin screw extruder. It could be shown that the rheological behavior as well as the blend morphology strongly depends to the type and the amount of the used coupling agent. A direct correlation between the rheological behavior and the blend morphology were expected but not confirmed. For this purpose, the particle size of the soft phase within the matrix was analyzed optically by a scanning electron microscope. Here, the thermal properties are only slightly affected, but in different ways. Fracture mechanical investigations were carried out to evaluate the blend modifications to the mechanical properties. The results obtained using the method of essential work of fracture showed a significant influence due to the type of coupling agent, but less due to morphology. Therefore, in order to understand the structural property relationships better, the selection of coupling agent is as important as the blend morphology.