AbstractThe development of magnetic hybrid films containing diblock copolymers (DBCs) and magnetic nanoparticles (NPs) by printing is a highly promising method for scalable and low‐cost fabrication. During printing, the drying and arrangement kinetics of the DBC and magnetic NPs play an important role in the film formation concerning morphology and magnetic properties. In this study, the morphology evolution of ultrahigh molecular weight DBC polystyrene‐block‐poly(methyl methacrylate) and magnetic iron platinum (FePt) NPs is investigated with grazing‐incidence small‐angle X‐ray scattering (GISAXS) in situ during printing. For comparison, a pure DBC film is printed without FePt NPs under the same conditions. The GISAXS data suggest that the addition of NPs accelerates the solvent evaporation, leading to a faster film formation of the hybrid film compared to the pure film. As the solvent is almost evaporated, a metastable state is observed in both films. Compared with the pure film, such a metastable state continues longer during the printing process of the hybrid film because of the presence of FePt NPs, which inhibits the reorganization of the DBC chains. Moreover, investigations of the field‐dependent magnetization and temperature‐dependent susceptibility indicate that the printed hybrid film is superparamagnetic, which makes this film class promising for magnetic sensors.