Blends of polypropylene and polyamide-6,6 have compatibilized with polypropylene that was carboxylated through a reactive extrusion process with an asymmetric functional peroxide. The compatibilized blends demonstrated a finely dispersed minor phase as shown by SEM. Because of the enhanced dispersion, additions of the carboxylated polypropylene to the blends resulted in a change in the crystallization nucleation mechanism of the PA-6,6 minor phase from heterogeneous to homogeneous in nature. A linear increase in the impact strength and significant enhancement in the tensile properties of the blends was observed with incorporations of the compatibilizer up to 30% of the matrix phase. In addition, the compatibilizing efficiency of the carboxylated polypropylene was compared to the of maleic anhydride functionalized polypropylene. When compared on an equivalent basis (total concentration of carboxylate or anhydride functionality added to the blend), the carboxylated polypropylene demonstrated a slightly better compatibiliziling efficiency than that of the anhydride functionalized polypropylene. The higher compatibilizing efficiency of the carboxylated polypropylene was attributed to a higher grafting efficiency of the carboxylation procedure as compared to the anhydride functionalization procedure.