Hafnium hydride is a promising material for next-generation nuclear reactors, particularly as control rods for fast fission and shielding in fusion systems. The material's intrinsic brittleness encourages its use in the form of hydride-metal composites, where the functional and mechanical performance is strongly influenced by the multiscale structure of hydride-matrix interfaces. In this study, we employ a suite of microscopy techniques, including scanning electron microscopy with electron backscatter diffraction, transmission electron microscopy with electron energy-loss spectroscopy, and atom probe tomography, to investigate the deuteride-matrix interfaces in a deuterium-charged Hf alloy. We characterise their structure and chemistry, extracting key information including the deuteride-matrix crystallographic orientation relationship, microstructural features, misfit-induced dislocation distributions, electron energy-loss characteristics, and the segregation of oxygen during deuteride growth. These findings help clarify the mechanisms of interface evolution and may contribute to improved understanding of hydride-metal systems, with potential relevance for their processing, performance, and design in nuclear applications.