Ghoncheh Ghavami, 25, was part of a group of women who tried to watch Iran play Italy in a match June 20, BBC reported.
The women were arrested and allegedly beaten before being freed. Ghavami was re-arrested later and subsequently put on trial.
Ghavami's mother, Susan Moshtaghian said that her daughter was striking against her continued detention without a court order, and the judiciary's decision to keep her case in limbo.
Her lawyer, Alizadeh Tabatabaie on Sunday said he had been shown court documents, which said Ghavami was found guilty of spreading anti-regime propaganda.
Ghavami is both a British and Iranian national
However, prosecutors have not confirmed Ghavami's sentence, her family said. She launched a hunger strike in October after being detained in an isolation cell.
"We have concerns about the grounds for this prosecution, the due process during the trial, and Miss Ghavami's treatment whilst in custody," UK Foreign Office said in a statement.
Ghavami is both a British and Iranian national. However, dual nationality is not recognised in Iran.
Iran banned women from volleyball games in 2012. The Iranian authorities have argued that women need protection from the lewd behaviour of male spectators.