As for many European cities, heat demand in Geneva is currently mostly supplied by individual fossil fuel boilers, contributing to an inefficient and non-sustainable energy system. However, the coming years will see major extensions of the existing district heating system, with inclusion of various renewable and waste heat resources. In this context, the geothermal potential of deep Mesozoic aquifers (500-2'500 m depth) is currently under investigation (exploration wells and 3D seismic survey). Preliminary results indicate a promising potential for thermal use. In this context, this study assesses how geothermal energy could be integrated into the main district heating system in Geneva, and therefore help decarbonizing the heat sector. An hourly based input/output model has been developed in order to generate district heating load curves and supply mix, from today until 2035, taking into account the foreseen evolution of the heat demand (new connections and buildings retrofitting), as well as the integration of various identified renewable resources. The results highlight that the deployment of geothermal energy is fundamental for a massive integration of renewables into the district heating supply. In a best-case scenario, its contribution could represent 22% of the district heating supply by 2035.