Fault zones localize a promising potential for the worldwide expansion of geothermal power generation, these systems must be considered and characterized from regional to fault scale. To develop new exploration projects, understanding the distribution of the geothermal reservoirs along fault zone is crucial due to the complex geometry of convection cells and the localized thermal anomalies associated. This is of particular importance in orogenic context, where the geothermal systems can be more heterogeneous due to the complex fault network inherited from the construction of the range and topography that can impact fluid flow. In the Eastern Pyrenees (France), the Têt normal fault localizes 29 hot springs, from 29 °C to 73 °C, distributed in four main clusters in less than 30 kilometers along the main fault. For these hydrothermal systems, fluids have a meteoric origin and reach at depth temperatures between 80 °C and 135 °C, which is variable according to the hot spring cluster. For this hydrothermal system, topography appears to be the main parameter to initiate hydrothermal circulation and control maximum fluid temperature at depth. In this study, we analyzed helium isotopes (3He/4He) in hot springs from the different clusters in order to identify the signatures associated to the geothermal reservoir. Isotopic ratios from the Têt fault hot springs vary from 0.03 and 0.10 R/Ra and do not correlate with water temperature. The data shows the same ratio for each hot spring cluster and a global increase of the isotopic ratio from East to West. These results are consistent with the major crustal thinning along the Têt fault that affects the eastern part of the Pyrenees and the Gulf of Lion. The differences in helium isotope ratios observed for the hot spring clusters along the Têt fault suggest the presence of distinct fluid reservoirs without fluid mixing. These results highlight the importance of detailed investigations to better characterize fluid reservoirs, particularly for fault hydrothermal systems in an orogenic context. In these systems, the thermal anomalies associated to fluid circulation can be local and several geothermal reservoirs can be distinguished at the scale of one fault.