Gamma radiation can have an influence on the integrity of the copper canisters used in deep geological repositories for isolating radioactive waste. Understanding the interactions between aqueous radiolysis products and container materials, particularly at the copper-water interface, is essential for assessing the canister integrity. This study investigates the gamma-radiation-induced products on copper specimens and water through experimental methods. Cu specimens were exposed to gamma radiation, and corrosion products were analysed using cathodic reduction, XPS, ICP-MS, and FT-IR. Results show that Cu2O is the dominant corrosion product formed during irradiation. Pre-oxidized Cu specimens, especially those formed at evaluated temperatures (140 °C), exhibited less corrosion depths and much more homogeneous coloration on the surfaces compared to literature data of irradiated bare Cu specimens and pre-oxidized 90 °C Cu specimens, suggesting the possibility that high temperature pre-oxidation enhances corrosion resistance under irradiation conditions. Additionally, the enhanced formation of alkane species, such as CH4, was observed in irradiated water, likely originated from the reduction of CO2 and HCO3− by radiation-induced reducing agents (H, H2, and eaq−). This observation raises new questions about the chemical transformations occurring under irradiation. The findings highlight the importance of understanding initial Cu oxide layer properties and suggest that optimizing temperature and environmental conditions in DGRs can improve the long-term performance of Cu canisters. Future studies are encouraged to explore localized corrosion mechanisms in Cl−-rich environments and to further investigate the implications of alkane production on the chemical stability of DGR systems.