This article investigates the impact of ancient tsunamis on the ancient World. Nowadays, the effects of such events on contemporary economic is easy to assess and investigate, thanks to the amount of information available. More complicated is the picture for pre-modem societies. The aim of this paper is precisely to focus on the economic consequences, if any, of tidal waves on certain regions and periods of the classical world. As a matter of fact, the study of natural disasters has been a popular topic for modem scholarship of the Antiquity. Along the Mediterranean basin, ancient tsunamis usually devastated regions with high levels of seismic activity, such as the Balkans, the South-East, the Levant or the central and eastern islands. Most of the archaeological evidence from tsunamis and earthquakes, however, has been mixed up by a combination of geological and human activity, making it difficult to single out which is which. Tsunamis were less frequent than earthquakes but their impact on human communities and their available natural resources could have been more catastrophic, at least in the short-term. The unexpected nature of such tidal waves surely produced considerable unrest within the affected population, who might have been familiar with the devastating effects of earthquakes but most probably were unaware of such a rare natural phenomenon. Our main goal, however, is to ascertain the economic impact of ancient tsunamis on the 'longue-durée'. The article is composed of two main parts. In the first one, we examine the evidence for tsunamis occurred in the Mediterranean basins from fifth century BC till the fourth AD, before the great tsunami of AD 365. It is possible to recognize how the Graeco-Roman literature describes, in some cases with remarkable accuracy, the basic functioning of what geologists know as tsunamis, but generally fails to provide any information on the economic impact of them on the ancient societies. In the second part, we focus on the tsunami of AD 365, for which we have more information, provided by both literary and documentary evidence, allowing us to use it as an interesting case study with a particular relevance in the ancient history. The final conclusion is that tsunamis in antiquity, as far as it is possible to infer from the status of our sources, despite having probably a huge damaging effect on the economy on the short term, usually did not affect it on the 'longue-durée', given, most likely, to efficient policies devised by ancient civilizations, to cope with such events.