The boat left Senegal on July 10 with 101 passengers on board, and 38 people were rescued on Tuesday, Senegal's foreign ministry said in a statement late on Tuesday.
It was not immediately clear when the incident occurred.
The survivors were on the Cape Verde island of Sal, where Senegal is liaising with authorities for their repatriation, the ministry said. One of the survivors was from Guinea-Bissau.
The Atlantic migration route from the coast of West Africa to the Canary Islands, typically used by African migrants trying to reach Spain, is one of the world's deadliest. Summer is its busiest period.
"Safe and regular pathways to migration are sorely lacking, which is what gives room to smugglers and traffickers to put people on these deadly journeys," said IOM spokeswoman Safa Msehli.
IOM is collecting information and did not yet have details about the latest incident, she added.
At least 559 people died attempting to reach the Canary Islands in 2022, while 126 people died or went missing on the same route in the first six months of this year with 15 shipwrecks recorded, according to the International Organization for Migration (IOM).
At least 15 people drowned when a boat carrying migrants capsized off the coast of Senegal's capital Dakar in late July.
(Reporting by Ngouda Dione; Additional reporting and writing by Nellie Peyton; Editing by Bernadette Baum)

A migrant from Senegal holds a mobile device showing a map he drew of the countries traveled through since leaving Africa toward the US in Tapachula, Chiapas state, Mexico, on Tuesday, April. 12, 2022. The number of African migrants trying to make it to the US southern border is on track to hit a potential record this year. By 2050, 86 million Africans will be displaced because of climate events. Photographer: Victoria Razo/Bloomberg via Getty Images