The Syrian Observatory for Human Rights said the 10 children and 15 women from Shiite towns in Aleppo province had been held by Islamist faction Jaish al-Mujahideen.
In a deal mediated by the Kurdish People's Protection Units (YPG), the women and children were released in exchange for Yousef Zawaa, a Jaish al-Mujahideen commander who was held by armed groups loyal to Syria's embattled regime.
The Britain-based Observatory said the women and children were from Zahraa and Nubol, two Shiite towns that have been under rebel siege for more than 18 months.
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"They were kidnapped more than a year when crossing checkpoints on their way from Nubol and Zahraa towards Damascus and Aleppo," said Observatory head Rami Abdel Rahman.
Zawaa was captured when he strayed into the pro-government enclave by mistake, Abdel Rahman told AFP.
Elsewhere in the country, the Observatory said government air strikes had killed at least 17 people, including five children, in Idlib province in the northwest.
Five of the deaths were in Idlib city, which was captured from government forces on March 28 by a coalition of Islamist groups, including Al-Qaeda affiliate Al-Nusra Front.