Citing survivors, the United Nations refugee agency UNHCR said 25 people were on board. Two survivors, one of whom is pregnant, were from Cameroon and the Democratic Republic of Congo, the agency said.
Hundreds of people have drowned trying to make the crossing since the refugee crisis began in 2015.
In that year, Lesbos was the main gateway into the European Union for nearly a million Syrians, Iraqis and Afghans.
At least 173,000 people, mostly Syrians, landed in Greece in 2016. The number of refugees and migrants in Greece has swelled to about 62,000 in the last year, about 13,000 of whom are in camps on five eastern Aegean islands waiting for their asylum applications to be processed.