Four migrants, including three children, died after their boat sank off the island of Leros in the southeastern Aegean Sea on Sunday, the Greek coast guard said.
The coast guard recovered the body of a woman and rescued at least 39 migrants who, according to their accounts, had sailed from Turkey, a coast guard official said.
The three children died after being hospitalised, the coast guard said. The nationalities of the migrants were not immediately known.
Along with Spain and Italy, Greece is one of the key entry points into the European Union for refugees and migrants from the Middle East, Africa and Asia.
Most asylum-seekers cross to Greece from neighbouring Turkey.