An increasing normal load scratch test was employed to study the scratch behavior of acrylic coatings. The effects of weathering and substrate surface roughness on the interfacial adhesion of acrylic-coated thermoplastic polyolefin (TPO) systems were investigated. The increasing load test gives valuable information regarding the onset location to failure and the critical normal load for interfacial delamination. Both flatbed scanner and scanning electron microscope are utilized to characterize the scratch-induced damage mechanism of the coated TPO system. An increase in weathering time and in surface roughness of the virgin TPO leads to the increase in scratch resistance of acrylic coating. In addition, with increasing weathering time there is an increase in discoloration, while a decrease in gloss occurs. The correlation between the change of scratch coefficient of friction and the onset location of interfacial delamination is discussed.