Coast guard officials said they rescued 75 people from the 17-metre vessel but government officials said they suspected more were trapped inside the sunken vessel and the death toll was likely to rise.
Video footage on the Turkish shoreline showed police walking among bodies of several dead as they washed ashore, among them a toddler lying on his back in navy blue clothing.
Today's deaths take the drowning total for January above 250, whereas the agency recorded 805 drowning deaths on Turkey-Greece smuggling routes throughout 2015.
A Turkish government official said he expects rescue workers to find more dead who were trapped inside the wreckage of the boat, which sank shortly after departing from the Aegean resort of Ayvacik, barely 8 kilometres north of the Lesbos coastline.
"We believe there are more dead bodies inside the boat," he told CNN-Turk television.
Ayvacik's mayor, Mehmet Unal Sahin, said most of the migrants were Syrians. The state-run Anadolu Agency said the boat also bore natives of Afghanistan and Myanmar.
In a statement, the Turkish coast guard said it dispatched three boats, a team of divers and a helicopter after receiving calls for help. The coast guard said its rescue teams recovered 33 bodies and were continuing to search.
Journalists at the scene said weather conditions Saturday on the Turkish coast were relatively mild, with light winds and temperatures around 12 degrees Celsius.
Joel Millman, a spokesman for the International Organisation for Migration, said the rate of deaths on Turkey-Greece human trafficking routes was "increasing at an alarming rate."
Millman, speaking before today's tragedy, said the rate of fatalities was running exceptionally high versus 2015. He said 55,000 had crossed by sea into Greece this month, a "very small number" versus the monthly flow in 2015.
