Blends of maleated polypropylene and maleated ethylene propylenediene (EPDM-g-MA) were compounded in a twin-screw extruder with a polyetheramine (PEA), polyoxypropylenediamine, as a compatibilizer. The effect of the compatibilizer concentration and molecular weight on the physical properties was investigated. FTIR data showed that the addition of the compatibilizer caused an imide linkage to form between the amine functionality on the PEA and the maleic anhydride (MA) functionality on both the polypropylene (PP) and the rubber backbone. This bond improved the interfacial adhesion between the rubber and the PP matrix, resulting in an improvement in the toughness of the blends. Other improvements in the physical properties of the blends with a compatibilizer compared to the blends without it included notched Izod impact, elongation at yield, and elongation at break. The optimum improvement in properties was found when the level of the compatibilizer was about 3 wt %. These changes in properties correlated well with the morphology observed via optical and scanning electron microscopy.