Reece Walsh said seeing his family watch him wear Australia's jersey for the first time made the anthem especially emotional.
"It's the first time that they're watching me put on the Aussie jersey."
Walsh, whose mother is of Māori descent and father is Indigenous, also became emotional during New Zealand's haka, he said.
His reaction came amid criticism after several Australian men's and women's players did not sing Advance Australia Fair before matches against New Zealand and Samoa at the Rugby League World Cup.
Some Indigenous players have explained their decision not to sing, while others may be focused on the match, according to the article.
Journalist Dean Ritchie said the sight made him "sick in the stomach"; Manly figure Peter Peters called it a "disgrace" and said players should be barred if they refused to sing.
Many social media users argued players were there to win, not compete in a singing contest.
After the Kangaroos' Thursday-night win, Cameron Munster told Triple M that Australia's players were proud to represent their country.
"We talk about culture and other nations, but we're very proud to wear the green and gold," Munster said. "It's something that we pride ourselves on."