Due to its thermo-physical properties, molybdenum is an excellent material for high temperature applications. Besides the thermal load, structural components for high temperature applications also have to withstand the mechanical load. In order to utilize entirely the high temperature potential for structural applications, e.g. X-ray rotating anodes for medical devices, it is essential to increase the strength of the molybdenum base metal. An effective way to achieve a higher strength at elevated temperatures is alloying with hafnium and carbon. The today’s increasing demand on materials for high temperature applications requires a detailed knowledge of their microstructural evolution during manufacturing and its impact upon the mechanical properties. On the one hand it was necessary to find cost efficient processing routes and on the other hand it was important to exploit the potentials of the material itself. Thus, the aim of the present doctoral thesis was to gain deeper understanding of the microstructure and its correlation to the strength of powder metallurgically manufactured Mo-Hf and Mo-Hf-C (MHC) alloys. The microstructural evolution during thermo-mechanical processing was investigated by X-ray diffraction, optical light microscopy, transmission electron microscopy and atom probe tomography. Furthermore, hardness tests, compressive and tensile tests were carried out during the mechanical characterization. The results received in this doctoral thesis are highly relevant for understanding the microstructural evolution during thermo-mechanical processing and in consequence, to influence the mechanical properties of the final MHC product.