This work presents the chemical and isotopic (delta O-18-H2O and delta D-H2O) composition of five thermal areas from the Atacama region (northern Chile), namely Laguna Verde, Juncalito, Termas de Rio Negro, Pante ón de Aliste, and Salar de Piedra Parada. The chemical and isotopic (He-3, He-4, delta C-13-CO2, and delta C-13-CH4) composition of gases bubbling from Juncalito is also reported. This work aims to (i) constrain the origin and physicochemical processes controlling the chemical and isotopic composition of bubbling gases and (ii) estimate the equilibrium temperatures of hydrothermal reservoirs. The thermal springs are fed by meteoric waters whose chemistry, during the underground circulation, is mainly controlled by water-rock interaction involving volcanic rocks and volcano-sedimentary sequences. Notable Li, B, and As enrichments are recognized, likely related to the leaching of hydrothermally altered andesitic to rhyolitic rocks and the presence of sedimentary sequences, distinctly below the Claudio Gay Cordillera. The He-3/He-4 ratios (similar to 1.4-1.5 Ra), within the range of the typical values for low-temperature hydrothermal gases from the Central Volcanic Zone, likely represent a mixture of an atmospheric endmember mixed with a differentiated cooling magma residing within the crust for a long time. The delta C-13-CO2 values suggest a dominant crustal CO2 source with a minor (1 %) mantle contribution. Chalcedony geothermometer provides reservoir temperatures up to 91 and 88 degrees C in Termas de Rio Negro and Laguna Verde, respectively. Further geophysical and geostructural investigations are recommended to constrain the source of heat in the Laguna Verde area, especially considering the presence of the quiescently degassing Ojos del Salado volcano.