Speaking to Premier from Islamabad, Mehwish Bhatti from the British Pakistani Christian Association said: "There are so many blasphemy victims - Christian victims - who are still in prison and are on death sentence like Asia Bibi".
Justice Nisar while reading out the verdict said, "The appeal is allowed. She is acquitted of all charges and if not required for any other charges she will be released forthwith".
Islamabad was put on high alert with extra security forces on Tuesday night ahead of the verdict.
A special three-person bench headed by Pakistan's top judge, Chief Justice Saqib Nasir, is due to deliver the verdict at 9am local time (0400 GMT), according to a notice by the court.
It has been ordered that Ms Bibi should be released if she has not committed any other crime. Bibi was later convicted of blasphemy and sentenced to death.
Ms Bibi's case has been high on the agenda of religious hardliners in Pakistan, many of whom are fiercely opposed to her release.
"It is great news for Pakistan and rest of the world", Bibi's lawyer Saiful Mulook told Reuters. She had gone to fetch water for herself and fellow farm workers on a hot day the previous year, but two Muslim women had refused to drink from the same container and she was accused by a mob of blasphemy. "We knew that she is innocent".
Ms. Bibi has always denied blaspheming.
At the Supreme Court hearing earlier this month - a hearing our legal team on the ground in Pakistan attended - Asia Bibi's defense attorney in Pakistan called much of the prosecution's evidence - or lack thereof - into question.
She was asked to fetch water, but the Muslim women objected, saying that as a non-Muslim she was unfit to touch the water bowl.
His announcement is a victory for human rights activists, who say religious minorities in Pakistan are routinely targeted and baseless allegations of blasphemy levied against them to settle personal vendettas.
Asia Bibi, a Catholic mother of five, was condemned to death in 2010 on charges of blasphemy.
The media has been prevented from discussing the case since the verdict was reserved on 8 October. Salman Taseer, the governor of Punjab province, was shot and killed by one of his guards in 2011 for defending Bibi and criticizing the misuse of the blasphemy law.
Ms Bibi's representatives have claimed she was involved in a dispute with her neighbours and her accusers had contradicted themselves.