Two bodies were found in the water off the coast of the island of Lesvos, while five others were recovered from the semi-sunken boat.
Greece's Merchant Marine Ministry said another eight people were rescued.
Authorities were still searching for two more migrants believed to be missing from the boat.
Three coastguard vessels, a helicopter and private boats were involved in the search.
The migrants' nationalities and details of how the boat sank were not immediately known.
Greece is a major transit point for illegal immigration into the European Union, with many making the journey to Greek islands from the nearby Turkish coast in small boats that are often overloaded and unseaworthy.
In January, 12 immigrants drowned when a boat overturned near the eastern Greek island of Farmakonisi.