David Fifita will make his Kangaroos debut against Fiji at Brisbane's Suncorp Stadium on Sunday, after a difficult year at the Titans.
In 2025, a recurring ankle injury drew criticism, while Fifita said the period was hard on him and his family.
The 26-year-old second-rower credited South Sydney coach Wayne Bennett, who gave him his NRL debut in 2018, with supporting him through a strong 2026 season.
Kevin Walters, his former Broncos assistant and Queensland coach when Fifita made his State of Origin debut in 2019, will coach him for Australia.
Fifita captained Australia's Prime Minister's XIII in a 60-10 win over Papua New Guinea in Port Moresby this month.
He previously represented Tonga at the 2022 World Cup to honour his late father.
"I loved putting the Tongan jersey on and I can't wait to put the Australian jersey on," Fifita said.