In the past, Mediterranean monk seals lived along the coasts of the Black Sea, throughout the entire Mediterranean Sea, at the Atlantic islands of Madeira, the Azores and Cape Verde. Along the northwestern coast of Africa the species lived from Morocco in the north all the way south to present Senegal and Gambia. The systematic hunting and persecution of the species over the past centuries appears to have been the main reason for the dramatic decline of the Mediterranean monk seal. The intensive killings that occurred in the last two centuries appear to have driven the species to extinction in the Black Sea and in most of the Mediterranean countries (including almost all of the countries in the southern Mediterranean Basin, as well as Spain, France and Italy in the northern Mediterranean Basin). Nowadays, the original distribution of the species has been significantly reduced and Mediterranean monk seals can be found only in four isolated, disjunct populations:
- A small population of approximately 40 individuals in the Archipelago of Madeira in the Atlantic Ocean.
- A colony of approximately 220 individuals on the Atlantic coast of northwest Africa at the Cabo Blanco Peninsula. A mass die-off occurred in 1997 that reduced that population by two thirds, and the colony has only partially recovered.
- A small population of perhaps fewer than 10 individuals along the Moroccan and Algerian Mediterranean coast. However, the lack of systematic monitoring and conservation actions in that area make the survival of this small population uncertain.
- The highest number of seals can be found in the eastern Mediterranean Basin, mainly in the Ionian and Aegean Seas in Greece and along the Mediterranean coasts of Turkey.
Recently, observations of monk seal individuals have been recorded in Israel, Libya, Cyprus, Croatia, Albania, Montenegro and Italy. This is a hopeful sign that the species will be able to return to its oldest areas of distribution.