Reaction-assisted diffusion bonding process of NiTi and Ti6Al4V was studied in situ. For this purpose, experiments were carried out at the High Energy Materials Science beamline (P-07) at PETRA-III (DESY). Ni/Ti multilayer thin films 2.5 μm thick with 12 and 25 nm modulation periods were directly deposited by magnetron sputtering onto the materials being joined. The NiTi and Ti6Al4V coated parts were placed with the films facing each other in a dilatometer equipped with Kapton windows for the x-ray beams. Microjoining was promoted by applying a 10 MPa pressure and inductively heating the materials, while simultaneously acquiring x-ray diffraction scans across the bond interface. Sound joints were produced at 750 °C. The formation of the NiTi2 phase could not be avoided.