Stefanie Imbruglia, a first cousin of pop star Natalie Imbruglia, told The Sun-Herald that legislation enacted three months ago prevented her listing an "intended" sex on her passport.
As a result, when she travels to Thailand in October, she will be required either to travel on a passport naming her as a man, Stephen Imbruglia, or on a document of identity that would leave her genderless.
"It is completely outrageous," Imbruglia, 42, told the newspaper.
"I may fly out to Thailand with a penis, but I'm going to come back as a total woman with a vagina, so how am I going to get through immgration on a male passport?"
After two years living as Stefanie Imbruglia, she is to spend 20,000 dollars (15,850 US) on gender reassignment surgery in Phuket.
The architect, from Banksia in Sydney's south, said she would be "psychologically damaged" if she travelled on a male passport.
But the alternative document of identity would not offer her the same level of protection and could lead to strip searches and harassment, according to a letter she received from the Department of Foreign Affairs and Trade.
Imbruglia also said her pop star cousin had been "very supportive" over her gender change.