It is uranium in water that controls our daily exposure, especially if drinking water is obtained from groundwater. Therefore in area strongly dependent from groundwater exploitation such as in warm climate contexts, the understanding of geological, geochemical and anthropogenic processes involved in U mobility is strongly required. This study aims at characterizing U concentrations and mobility in the Recife´s groundwater (Pernambuco state, NE Brazil.), exploited from a multi-layered sedimentary aquifer system. Due to population increases and climate change impacts, groundwater resources are highly strategic for the coming decades and their quality needs to be evaluated. In this perspective, chemical analyses of major and traces elements, including U, were performed within the superficial and deep aquifers. The results show a high variability in mobile U, implying heterogeneity of sources and processes. Coupled with a lithological description of the area, geochemical modeling was carried out, aiming at evaluate possible speciation processes. It appears that the different lithologies, inherited from plutonic, metamorphic and sedimentary rocks may primarily explain the presence of U. In addition, immobilization by hydroxyferrous oxydes may occur, controlled by pH and pE and amount of iron present in the system. When these parameters are affected, U may be mobile in the form of Uranyl ions (low pH) or associated to free carbonate complexes (high pH). As these preliminary conclusions are still based on hypothesis about the abundance of iron, this study highlights the importance of a detailed knowledge of aquifer mineralogy to better understand U mobility constraints in groundwater. This should permit to better manage the resource of increasing importance in this kind of hotspot of climate and anthropogenic pressure.