High-entropy alloys (HEA) gained a lot of scientific attention in the last two decades. The possibilities of this multi-principal element alloying are vast. Within this vastness of alloy systems, the hitherto unresearched, equimolar TiZrTaVSi system was selected for this thesis with the intention to obtain mechanically hard and thermally stable metallic and nitride coatings by cathodic arc evaporation of a single HEA cathode. This thesis also studied the impact of various deposition process parameters on the properties of the metallic and nitride coatings in terms of composition, surface properties, mechanical properties and crystallographic structure. Furthermore, droplet distribution and angular distribution of the species of the deposition flux were studied. The thermal stability and oxidation resistance were analysed in detail by DSC/TGA and in-situ high temperature XRD. The results showed very good mechanical properties of the nitride coatings in the as-deposited state. The conducted analyses within this thesis point to microstructures which are composed of extremely fine, nanocrystalline grains. Both the nitride and metallic coatings consisted of only a single phase, fcc for the nitride and bcc for the metallic coatings, which corresponds well to the findings published on many other HEAs investigated in literature. These two main phases remained stable until ~600 °C in ambient air, which marked the onset of oxidation, irrespective of the coating composition. The coatings showed no signs of instability for temperatures up to 1200 °C in vacuum; the metallic coatings even revealed an astonishing doubling of both hardness and elastic modulus compared to the as-deposited state. Herein may also lie possible applications in oxygen depleted environments.