Manu (26), the Highlanders co-captain, has signed a two-year deal with Edinburgh, and will leave for Scotland at the end of the Super rugby season.
The big No 8 has played 71 Super rugby games, including 54 for the Highlanders, and has been one of the best for the southern franchise in recent seasons.
Highlanders general manager Roger Clark said Manu had provided outstanding service to the team and been a hard worker for many years.
''We have always had an understanding with Nasi that he really wanted to be an All Black. If that was not going to happen then we knew the chances of retaining him were always going to be difficult,'' Clark said.
''He had many offers from overseas clubs and has picked up a good deal.''
Manu first joined the Highlanders in 2010 and was named co-captain last season.
He has been a consistent performer for the team and his ability to make the advantage line and get around the field has been critical to the Highlanders' improvement over recent seasons.
A foot injury forced him to miss all but 40 minutes of the 2013 season and that had plenty to do with a disappointing Highlanders season.
Manu was a schoolboy star out of Christchurch Boys' High School, and played first-class rugby before he played club rugby.
He has played 65 games for Canterbury.
Despite his stellar form over the past few years, Manu has never been in the All Black picture.
The likes of Kieran Read, Victor Vito, Jerome Kaino and Liam Messam appear to be ahead of Manu in the No 8 pecking order.
Manu told the Otago Daily Times earlier this season he was not interested in playing for another country and just wanted to play for the All Blacks.
Manu is of Tongan heritage but was born in New Zealand.
He will join former Highlanders back Phil Burleigh at the Edinburgh club while former Hawkes Bay captain Mike Coman is also at the club.
Former Otago flanker Hugh Blake was at the club but has moved to the Glasgow club until the end of the northern hemisphere season.
Blake was included in the Scottish side for the Six Nations.
• The Highlanders will not be calling in any additional coaches despite assistant coach Scott McLeod tearing his Achilles.
McLeod suffered the injury last Friday playing squash. He had an operation on Sunday and will be out of action for some time.
Clark said some of McLeod's work could be done away from the training paddock while Jon Preston had been the coach on the paddock last Friday night for the match against the Hurricanes, and would continue in that role.