"Only one person was plucked out of the water and hospitalised," a ports police spokeswoman told AFP on Saturday, saying 18 bodies had been found so far - most on a beach near the town of Mytilene on the island of Lesbos.
The known lone survivor, a 20-year-old man taken to hospital in Mytilene, told authorities the boat was carrying 28 people including children.
Three port police boats resumed the search on Saturday in the hope of finding more survivors.
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The victims set sail from the western coast of Turkey on Thursday but ran into bad weather that sank their boat, ports police said.
Authorities have not yet released the victims' nationalities.
The island is one of several in the eastern Aegean sea near the Turkish coast and are frequent targets for migrants trying to reach western Europe.
Migrants often perish trying to make the crossing in makeshift boats, particularly in winter.
