Starch-based polymer blends are able to alleviate the environmental concerns. However, they usually suffer poor mechanical properties. Here, we first prepared plasticized starch using diethanolamine as a reactive plasticizer and then fabricated polypropylene (PP)/starch blends using maleic anhydride-grafted PP (MAPP) as the compatibilizer. It is found that the size of the starch domains gradually reduced with increasing MAPP loading, indicating significantly improved interfacial compatibility. Adding 15 wt % MAPP can basically retain the tensile strength and considerably enhance Young's modulus, the bending strength, and the modulus of polymer blends relative to PP and its blends without compatibilization. Additionally, the glass transition temperature of PP is increased by 4.9 degrees C for the PP blend with 30 wt % MAPP. These largely enhanced mechanical properties are mainly attributed to improved interfacial adhesion. Our work provides a facile, effective strategy for reducing the environmental impact of the use of nonbiodegradable plastics.