The Greek seas as a part of the Eastern Mediterranean Sea, have been considered as a hotspot for the entrance of non-indigenous species (NIS). Ballast water functions as a major pathway for the spread of NIS in new environments, posing significant threats to both the ecosystems and human health. Nine non-indigenous fish species, originating from the Red Sea, have been introduced to the Greek seas since 1925. Despite the implemented laws for limiting the spread of NIS and the subsequent impacts, current global environmental issues, such as climate change and micro-plastic pollution, could result in a rapid spread and establishment of NIS in hot-spot regions, including the Greek seas. A more systematic use of advanced tools for the systematic monitoring of all NIS in the Mediterranean Sea is necessary.