The 35-year-old appeared in the Manukau District Court this morning.
He was due to stand trial this week on charges of importing methamphetamine and possessing methamphetamine for supply.
But he has now entered a guilty plea through his lawyer Vivienne Feyen to a representative importation charge.
Feyen told the court Vatuvei accepted responsibility for his offending.
Vatuvei has been remanded on bail ahead of his sentencing in December.
The Crown has indicated it will withdraw the remaining charges at sentencing.
Vatuvei was arrested in November 2019.
He fought to keep his name secret, but name suppression was declined by both the District Court and High Court.
Days before suppression was due to lapse, Vatuvei outed himself on Instagram.
At the time, he told his followers he wanted them to hear directly from him that he was accused of possessing and importing the drug in 2019.
"I'll be fighting my innocence for these charges," he said.
"I know there'll be a lot of questions that will be wanting answers but I've been advised by my legal team that's all I can talk about. So hopefully you can all respect that, and also can you please respect the privacy of my family while I go through this battle."
Between 2004 and 2017, Vatuvei played 14 seasons for the Warriors and scored 152 tries over 226 games.
He was nicknamed "the Beast" and became the first player in NRL history to complete the feat of scoring 10 tries or more in 10 consecutive seasons in 2015.
In 2019 he had success in Dancing with the Stars, winning the series with dance partner Loryn Reynolds.