Eutectic high entropy alloys (EHEA) possess attractive properties such as exceptional strength/ductility balance and high castability. The former is achieved by the two-phase nature of these alloys consisting of a hard, BCC-like phase and a soft, FCC-like phase. The balance can even be improved by thermo-mechanical processing of the as-cast, lamellar structure. Research towards the interaction with hydrogen is, however, limited for this new type of alloys, yet needed for its future potential. In this project, AlCoCrFeNi2.1 EHEA will be cast and thermo-mechanically processed in two different ways to vary the phase distribution and morphology while maintaining excellent mechanical behaviour. The hydrogen characteristics will be assessed with thermal methods and numerical diffusion modelling. Atom probe tomography measurements are envisaged to visualise trapping at phase boundaries and precipitates. Moreover, micro-mechanical tensile testing and micro-pillar compression testing will be executed with and without the presence of hydrogen to evaluate its effect on the mechanical performance. To reveal the mechanisms behind the interaction with hydrogen, the deformed EHEA will be thoroughly investigated with high-level microscopy techniques, such as electron backscatter diffraction, electron channeling contrast imaging and transmission electron microscopy, aided by sample preparation with focused ion beam.