They were among more than 160 Kurds abducted as they travelled east through Syria en route for Iraqi Kurdistan, according to the Syrian Observatory for Human Rights.
The hostages were held in the jihadist stronghold of Raqa, accused of being members of the Democratic Union Party (PYD), the main Kurdish political party in Syria.
It was unclear why they were freed, according to the Britain-based Observatory.
PYD fighters have been defending Kobane against an IS attack for the past seven weeks, and the town has become a prominent symbol of resistance to the jihadists.
The Syrian Kurds have been reinforced by opposition rebels and Iraqi Kurdish peshmerga fighters.
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Of the freed hostages, 53 were able to cross into neighbouring Turkey while 40 were still in Syria, said the Observatory, which relies on a broad network of activists for its reports.
About 70 others remain in captivity.
IS has seized large parts of Syria and Iraq, proclaiming an Islamic caliphate and committing widespread atrocities.
Kidnapping is rife in Syria with IS and other extremists abducting rival fighters, journalists, aid workers, soldiers and civilians.
Late last month, IS released about 25 Syrian Kurdish schoolchildren.
They were the last to be freed from a group of 153 schoolchildren kidnapped by IS in the northern province of Aleppo in May after sitting exams.