The south Aegean volcanic arc and Ikaria island are characterised by the presence of many thermal springs. Hydrochemical data from 46 springs were used to get insight on their water quality. Highest temperatures were recorded in Ikaria (58.3 °C), Santorini (50 °C) and Milos (43.7 °C). There is a wide range of major ions’ concentration but the predominant water type is Na-Cl. The composition of waters is mainly influenced by seawater intrusion and secondly by mixing with deep hydrothermal and shallow meteoric waters. The trace elements’ concentration is mainly controlled by high temperature dissolution of primary volcanic minerals and precipitation of secondary solid phases. Factor analysis explains 90% of the total compositional variance with a five factor model.