We have investigated microstructure and properties of diamond composite coatings on cemented tungsten carbide tool substrates, and compared wear resistance of these coatings with that of polycrystalline diamond (PCD) and polycrystalline boron nitride (PCBN) tools brazed on to cemented tungsten carbide substrates. The diamond composite coatings consist of layers of discontinuous diamond, TiC, and continuous diamond. In these composite layers, diamond is deposited by hot filament chemical vapor deposition and TiC by pulsed laser physical vapor deposition. Thermal stresses in the composite layer and the substrate are reduced and thereby help to improve the adhesion of diamond to the tool substrate. These tool coatings are characterized by scanning electron microscopy, Raman spectroscopy, secondary ion mass spectroscopy, and x-ray diffraction. The results of microstructural characterization and analysis of chemical composition are correlated with wear resistance. The present results demonstrate the advantages associated with composite diamond coatings compared to PCD and PCBN tool coatings.