In a comparative study of the influence of thermal annealing processes on TiN and TiAlN coatings prepared by DC magnetron sputtering, we characterized the samples by using x-ray diffraction and scanning electron microscopy. The annealing temperature significantly affected the structural properties of the coatings. The TiO2 phase was generated in the TiAlN coatings by thermal annealing at a higher temperature than in the TiN coatings.