Interfacially compatibilized immiscible blends with an isotactic polypropylene matrix (PP) and dispersed polyamide-66 (PA) were prepared by extrusion with anhydride-grafted isotactic PP compatibilizers, one of high-anhydride content (HAC, 2.7 wt % grafted maleic anhydride) and one of low-anhydride content (LAC, 0.2 wt % anhydride). On a weight basis, HAC was more efficient than LAC in dispersing PA to submicron domains, but on a total weight % anhydride basis, both compatibilizers were equally efficient. Both compatibilizers imparted similar tensile strength improvement compared to an uncompatibilized blend. Maximum fracture strain was obtained at similar total anhydride content, but much higher maximum fracture strain was achieved with LAC than with HAC. Good adhesion in an 11.25 wt % LAC blend was seen at the microscale as fibrillar ligaments connecting PA particles to the drawn PP matrix. Interfacial failure was observed in a lower fracture strain composition, 11.25 wt % HAC.