Nanostructured and conventional WC-Co coatings were deposited by vacuum plasma spraying. The wear and friction properties of the two coatings against alumina under dry friction conditions were comparatively studied. It was found that the wear resistance of the nanostructured WC-Co coating is superior to that of conventional WC-Co coatings, especially under high load conditions. The improved wear resistance of the nanostructured coating is attributed to its higher hardness and toughness. The wear mechanism of the nanostructured WC-Co coating is plastic deformation with slight surface fracture, whilst that of a conventional WC-Co coating is the initial removal of a binder phase followed by fragmentation or uprooting of carbide grains. Their tribological properties are discussed in relation to the microstructure of the two coatings. It is concluded the decomposition is a fatal factor influencing the wear resistance of thermal sprayed nanostructured WC-Co coatings.