Both TiC and TiN are materials commonly used as coatings or interlayers for tools like cutting inserts or drills. They are taken either as top layers to enhance the wear and oxidation resistance, or as intermediate and base layers to improve the adhesion of other layers. For the use as base and interlayers, the thermal expansion is an important property. This property can be modified by combining the two named materials to Ti(C,N). In this work, the thermal expansion of Ti(C,N), varying from pure TiC to pure TiN in equal steps of [C]/[C+N], was determined. Therefore, after deposition by nonreactive magnetron sputtering, the substrate was removed by etching and the coating materials were powdered. Subsequently, the powder was investigated by high temperature X-ray diffraction in the temperature range of 25 to 1000 °C. From the diffractograms, the lattice parameters and consequently the lattice expansion were determined. In order to obtain precise values for the thermal expansion of the sputtered materials, the high temperature unit of the diffractometer was carefully calibrated by measuring the thermal expansion of a Pt powder and the direct temperature measurement by a thermocouple. A maximum temperature deviation of up to 20 °C was observed and corrected for by the determination of a correctional polynomial function. The lattice parameter of the Ti(C,N) samples showed an approximately linear increase with increasing C content from 4.246 Å for TiN to 4.322 Å for TiC at 25 °C. The temperature dependence exhibited a parabolic behavior between 25 °C and 1000 °C, where the values increased to 4.286 Å for TiN and 4.355 Å for TiC at 1000 °C. The linear thermal expansion coefficient of Ti(C,N) increased from 7.5 ∙ 10-6 °C-1 for TiC to 8.1 ∙ 10-6 °C-1 for TiN at 25 °C. Going to 1000 °C, the values increased up to 8.3 ∙ 10-6 °C-1 (TiC) and 11 ∙ 10-6 °C-1 (TiN), respectively. The thermal expansion coefficient of Ti(C,N) exhibited an approximately linear behavior over composition as well as over temperature. When comparing the obtained results with the results for hot pressed samples, in general a good agreement was found. The main difference was that the thermal expansion coefficients for sputtered Ti(C,N) exhibit less variation over temperature. In conclusion, high temperature X-ray diffraction was successfully used to determine the thermal expansion of magnetron sputtered Ti(C,N). This subsequently enables the adaption of the expansion coefficient to the scope of a particular application by tailoring the composition. The obtained results could be corrected by the high temperature calibration and corroborated by the comparison with the data gained by an extensive literature research.