British-Iranian Ghoncheh Ghavami, who was detained after attempting to watch a men's volleyball match in Iran, has been freed on bail, her family says.
Ms Ghavami was freed because of health problems and was staying with her parents in Tehran awaiting a decision by the Court of Appeal, they said.
Ms Ghavami, 25, was part of a group of women arrested after trying to watch the match on 20 June.
Iranian prosecutors have since accused her of having links to the opposition.
Ms Ghavami has staged hunger strikes against her detention, while hundreds of thousands of people have signed a petition calling for her release.
Her brother, Iman Ghavami, told the BBC's Newshour that their parents - who are in Iran - had wanted to ask for a full medical check-up because Ms Ghavami had "intestinal problems".
Mr Ghavami said his sister had served five months of a one-year sentence and that the release "was quite unexpected but a welcome move".
"Everyone is happy - my parents and my sister. There are many possibilities, we're not really sure what's going to happen, but we hope for the best outcome.
"For the time being... it's her 26th birthday tomorrow morning, so I think they're going to celebrate for a day or so."
Iran's Sharq newspaper said on its Twitter account (in Persian) that she was released after paying bail amounting to $38,000 (£24,000).
Ms Ghavami and the other women were arrested and allegedly beaten after attempting to watch Iran play Italy in a volleyball match.
They were later freed, but Ms Ghavami was rearrested later and subsequently put on trial.
Iran banned women from men's volleyball games in 2012, extending a long-standing ban on football matches.
The Iranian authorities have argued that women need protection from the lewd behaviour of male fans.
Ms Ghavami has held hunger strikes in prison, protesting against what she called her illegal detention.
There had previously been confusion over Ms Ghavami's situation.
Her lawyer said on 2 November that he had been shown court documents that said Ms Ghavami was found guilty of spreading anti-regime propaganda.
However, prosecutors did not confirm her conviction, prompting her family to accuse the judiciary of keeping Ms Ghavami's case in limbo.
Prosecutors then told Isna news agency on 18 November that Ms Ghavami's case was under review, and that she had been charged for taking part in opposition protests abroad, not for attempting to watch the match.
On Saturday, Ms Ghavami's family said they had seen the verdict, and that Ms Ghavami had been given a two-year travel ban in addition to a one-year jail sentence.
Ms Ghavami's MP in Hammersmith, London, welcomed the news, describing her as "a young woman of great courage".
Andy Slaughter said "we must continue the campaign until charges against her are dropped and she is free to travel outside Iran".
Dual nationality concerns
The UK Foreign Office has previously expressed "concerns about the grounds for this prosecution, due process during the trial, and [Ms] Ghavami's treatment whilst in custody".
Ms Ghavami is both a British and Iranian national. However, dual nationality is not recognised in Iran.
The British government recognises dual nationality.
However, under international law, countries cannot offer formal diplomatic protection to their nationals if they are in a second country where they also hold nationality.