The women said they were treated well by the rebels which appeared to be the case in a video of their release issued by the al-Qaeda group.
It showed a masked gunman carrying one elderly nun who was too weak to walk to a waiting vehicle.
Rami Abdurrahman, of the Britain-based Syrian Observatory for Human Rights, said the release came in exchange for 150 female prisoners and three children held by the government.
Residents gave the nuns a warm welcome at the Church of the Cross in the predominantly Christian neighbourhood of Qassaa, state news agency Sana reported.
They were released in a rare deal between the Syrian government and rebels of the so-called Nusra Front that was mediated by the Gulf country of Qatar, traditionally a rebel supporter.
The video of the nuns’ release appeared genuine, diplomatic experts said. The dialogue between the nuns and the armed, masked Sunni militants showed a surprising familiarity in the way they addressed each other.
“What we did was less than what we should have done,” an off-camera rebel voice said to a nun, presumably referring to the length of their captivity. He said that God would reward the nuns for their suffering.
“May God reward every person who sought to resolve this problem,” said a nun, who later exclaimed: “Four months, man.”
As the women reached the car, the unseen rebel said: “I was so happy to be in communication with you and I hope that we can stay in communication, if God decides that. Please say hello to your families for me, and I hope you arrive safely.”
In Damascus, the nuns prayed before heading to the Greek Orthodox Patriarchate in Old Damascus, where they will now stay, Sana said.
Bishop Luca al-Khoury, who led an official church reception to greet the nuns, accused the rebels fighting to overthrow president Bashar al-Assad of targeting Syria’s patchwork of religious minorities. Bishop Al-Khoury is a frequent defender of Mr Assad’s rule.
He said: “Syria, which does not differentiate between Muslims and Christians, is targeted … by the armed terrorist groups who don’t understand anything but the language of killing and destruction.”
Although the nuns appear to have been treated well, their seizure confirmed the fears of many Syrian Christians that they were being targeted by rebel extremists in the increasingly sectarian three-year conflict.
The country’s mix of rebel groups is overwhelmingly Sunni Muslim, while minorities include Christians, Shiite Muslims and Alawites – whose sect is a Shiite offshoot. Most have sided with Mr Assad, or remained neutral, fearing for their fate should rebels take power. Mr Assad is an Alawite.
Two bishops were seized in rebel-held areas in April, and an Italian Jesuit priest, Father Paolo Dall’Oglio, went missing in July.