The effects of substrate surface treatment on TiAlN PVD coating on submicron cemented carbide was investigated. Surface roughness and morphology were improved by physical treatment such as micro blasting, brush lapping and plasma etching with decreased Co content in the surface layer. The Co content in the surface does not seem to affect coating adhesion or the quality considerably. The smoother surface induced by the surface treatment improved TiAlN adhesion and surface roughness. The insert treated by blasting and lapping before coating showed a better cutting performance than those with ultrasonic treatment. It was concluded that the substrate surface characteristics are closely related to the performance of the TiAlN coated inserts.