Amilia Radevska bypassed increased security and approached the singer at the end of his appearance on the show, according to Herald Sun.
Radevska is said to have kicked and shouted "stop it Brian", and was then restrained by McFadden while host Grant Denyer interviewed Bieber.
"I was looking around and saw a crack in security and thought 'Now or never," 14-year-old Radevska said. "He told me he loved me and it was all okay before I was dragged away."
It is unknown whether the pre-recorded footage of Radevska's attempted stage invasion will feature in the next episode of Australia's Got Talent when it airs on Wednesday (July 18) at 7.30pm on the Seven Network.
Bieber fans have also been staking out the Olsen Hotel in Melbourne where the star is staying.
Bieber is currently being sued for over $9 million (£5.8 million) by a woman who claims she sustained permanent damage to her ears after attending one of his shows.
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