Savea, who played club rugby in Japan in 2024, said he was sad to end more than a decade's association at Wellington Hurricanes.
The All Blacks back-row forward believed the time was right to honour his Samoan family and "give back to my heritage".
Savea's deal with Moana Pasifika is for three seasons and leaves him eligible to represent New Zealand through to the 2027 Rugby World Cup in Australia.
Auckland-based Moana are made up of players with a Pacific islands family background, including Savea's older brother Julian, a former All Blacks wing who switched from Hurricanes last year.
Moana will hope the dynamic Savea, who has played 84 times for New Zealand, can change their fortunes, with the club having struggled since joining Super Rugby for the 2022 season.
They finished last in their first two seasons and second-last in 2024, winning only five of their 42 Super Rugby matches.
Savea's parents were both born in Samoa and migrated to New Zealand when he was a child.
"I think it's the right time for a change and I spent a lot of quiet time with my family thinking about things before making this decision," Savea said.
"It will be huge to give back to my heritage and my culture in such a meaningful way.
"My brother Julian has told me that this team was made for us so I can't wait to get started."
Savea was crowned the world's top player in 2023 despite the All Blacks falling one point short of beating South Africa in the World Cup final in Paris.
The 30-year-old All Blacks vice-captain led the haka for the first time before New Zealand's 47-5 win over Fiji in San Diego on Saturday where he scored his 26th international try.
New Zealand coach Scott Robertson said Savea was an inspirational figure.
"Ardie brings a huge amount of passion, care and mana (leadership) to the All Blacks environment," he said.
"He has led through his actions over a long period of time and has inspired his teammates with the way he's represented his country, community, culture and family."
Savea has played 131 games for the Hurricanes since his debut in 2013.
He did not feature in Super Rugby in 2024 after opting for a short-term sabbatical with Kobe Steelers after the end of last year's World Cup in France.
