The Tuzlukçu geothermal area is 25 km northeast of Akşehir (Konya/Turkey). The aim of the present study is to determine the hydrogeochemical and isotopic characteristics (δ18O, δ2H, 3H, and 13C) and reservoir temperatures. The electrical conductivity values of thermal waters with temperatures ranging between 48° and 56°C are between 3200 and 8795 μs/cm. The sampled waters are of the Ca–Mg–HCO3 and Na–HCO3 types. The chemical composition of the waters is mainly controlled by the dissolution/weathering of carbonates and silicates and reverse ion-exchange reactions. The calculated quartz geothermometers were 70–90°C for Tuzlukçu thermal waters. The thermal waters’ isotopic data (δ18O, δ2H and 3H) shows mixing, intermediate to the deep circulating meteoric origin, and 20–80 years of residence time. The 13C ratio of the water varies between −10.92 and 5.24. There are multiple carbon sources in cold waters, whereas the primary carbon sources in thermal waters are the dissolution of marine carbonates and metamorphic CO2.