Zahra Ghanbari became the fifth member of the team to change her mind after initially taking up an offer to stay in the country at the end of the AFC Women's Asian Cup.
Her decision was seized on by the Iranian state news agency IRNA, which has hailed the return of all but two players from Australia as a coup for the under-siege regime.
But former Iranian soccer player Shiva Amini said she had received information from Australia that the Iranian Football Federation, alongside the Islamic Revolutionary Guard, had placed "intense and systematic pressure" on the group's families.
This included targeting the family of Ms Ghanbari, whose father had recently died.Â
"This shows the level of cruelty and desperation they are willing to use to force these athletes to comply," Ms Amini wrote on social media platform X.
"Through the team's manager, who presented herself to the players as someone they could trust and rely on, they were able to persuade some of the players to return.
"Several of the players decided to go back because the threats against their families became unbearable and the intimidation was relentless."
The soccer player turned human rights activist said the team urgently needed support and protection.
Home Affairs Minister Tony Burke previously announced three members of the group had decided to leave despite the government doing everything it could to ensure the women were protected.
Seven members of the Iranian soccer group, including six players and one support staff member, were initially granted humanitarian visas to remain in Australia.
Cabinet minister Catherine King said the government understood the "very difficult" decision members of the group were making.
"They would have been facing enormous pressure from what was happening overseas, in their home country as well," she told ABC Radio on Monday.
"They were provided an opportunity here to come to Australia to make that decision, and ultimately, it is their choice, and I think that Australia can be very proud as a country that we were able to do that."
The team left a Gold Coast hotel on Tuesday afternoon under police guard with one player reportedly dragged by her wrist by a fellow teammate onto a bus.
There are fears for the rest of the team's safety on their return to Iran after they were labelled "wartime traitors" on state media for refusing to sing the national anthem before their opening match.
Conflict in the Middle East continues to widen with intensified attacks on Iran by the US and Israel and retaliatory strikes targeting multiple Gulf countries.
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