Mullah Abdul Salam Zaeef, who served as the Taliban's international spokesman in the early days of the US bombing campaign in 2001, was shown on Afghan state TV meeting the head of Afghanistan's peace and reconciliation commission, Sibghatullah Mujaddedi on Monday.
The TV report said Zaeef had been released from Guantanamo as a result of the commission's efforts.
It did not say when he had been released, and commission and other officials could not immediately be reached for comment.
Zaeef became the voice of the Taliban after the US launched its air campaign in October 2001 in retaliation for the September 11 attacks.
He held frequent news conferences at the Afghan embassy in Pakistan that were broadcast worldwide.
The Pakistani government eventually ordered Zaeef to stop the news conferences.
After Taliban rule collapsed in December 2001, he sought political asylum in Pakistan but was arrested the next month and transferred to a US detention facility in Kandahar, Afghanistan.
Relatives said in August 2002 that he was being held at Guantanamo Bay.
The Guantanamo Bay prison still
holds about 520 prisoners
The prison at Guantanamo Bay opened in January 2002 and now holds around 520 prisoners, many captured during the US-led war in Afghanistan.
More than 230 others have been released or transferred to the custody of their home governments.
Early last month, Afghan and US officials said Afghans held in US military custody at Guantanamo and elsewhere would gradually be sent back to Afghanistan, where they would be in "exclusive custody and control" of the US-backed government.
At the time, a Pentagon spokesman said the US military was holding about 110 Afghans at Guantanamo and 350 at a detention centre in Bagram, the main US base in Afghanistan.
The detainees could eventually be transferred to Afghan government control.
The Afghan government has so far not imprisoned Afghans released from Guantanamo.