Epitaxially grown Cr(N,O) thin films were prepared on MgO substrates, with a misfit of -1.7% with respect to CrN, using pulsed laser deposition. X-ray diffraction patterns showed the peak for the (200) reflection of Cr(N,O) around the peak for the (200) reflection of MgO. The X-ray diffraction pattern of the phi scan for the (111) reflection of Cr(N,O) showed a narrow peak appearing every 90 degrees. From microstructural observations, grain boundaries in the thin films could not be confirmed. In order to evaluate the oxidation behavior of Cr(N,O) thin films, oxidation tests in air were carried out. After the oxidation tests, a Cr2O3 phase was formed at 873K and the B1 (NaCl-type) phase disappeared at 1173K. In the thin film oxidized at 1073K, a Cr2O3 layer on the surface of the thin film as well as a compositional gradient of oxygen were observed. This indicates that Cr(N,O) hard coatings can form oxidation barrier layers to extend the lifetime of cutting tools.