The Aegean Sea, due to the complexity and variety of morphological features, bathymetry, hydrological, hydrodynamic features and climatic characteristics, offers a unique opportunity for monitoring the spreading and/or invasion of alien biota. It is known that the establishment of warm/tropical marine alien species is related mainly to the increase in sea temperature. A significant increase in aliens' number along the southern Aegean (Dodecanese) coasts has been documented in the last twenty years, while their arrival has produced evident changes in coastal ecosystem composition and function. Although the study area acts as a crossroad for tropical alien species introduction in the eastern Mediterranean Sea, a direct attempt to link temperature alterations with new alien species arrivals has not been performed. Satellite and in situ derived marine temperature data showed that the study area has gone through a remarkable warming, while the link between global temperatures and regional ones revealed that this warming is not a local phenomenon but part of global climate trends. Examining relationships between new alien species arrivals data since 1929 against global temperatures, it is shown that their introduction rate parallels the significant increase of marine temperatures. The association of alien introductions with marine water warming, as well as potential effects on ecosystem functioning of selected species is discussed.