Within this thesis, different strategies for film synthesis and alloying are proposed to design Mo-based thin films with enhanced fracture resistance for their future application in flexible electronics. Advanced in situ characterization techniques in laboratory and at synchrotron large scale facilities were combined to allow a sophisticated analysis of the deformation mechanisms and fracture behavior of polymer-supported Mo and Mo-based thin films. The findings emphasized a strong dependence of the fracture properties on the synthesis conditions of the sputter-deposited Mo thin films. By tailoring their residual stress state, a considerable improvement in crack onset strain was achieved. Moreover, it was demonstrated that both fracture strength and crack onset strain of Mo thin films scale with the film thickness. Since all Mo thin films exhibited a distinctly brittle fracture behavior, alloying with Re and Cu was explored as feasible concepts to overcome their poor ductility. A substantial toughness improvement with rising Re content up to the solubility limit was obtained, which stems from the increased plasticity and bond strengthening in the Mo-Re solid solutions. Furthermore, it was observed that Cu addition to Mo results in an increased ductility, which was rationalized by the low shear resistant bonding in Mo-Cu solid solutions. In general, both concepts proved to be promising in order to enable the utilization of Mo based thin films in flexible electronics.