Vainikolo (23), has signed a two-year deal with Otago and hopes to become the province's next All Black.
The winger said he was really looking forward to getting back to Otago and enjoying the southern hospitality.
"The guys were a lot of fun and coaches did a real lot for me," Vainikolo said.
"But I still have plenty to work on [with] my game. Just how to read a game. I've got a lot to learn and playing more rugby at that level will help me."
Vainikolo said the ultimate goal was the All Blacks and he knew he had to bring consistency to his game to reach higher honours.
He said he was always going to transfer to Otago, but negotiations had taken a while as he did not want to leave Northland in the lurch.
"I owe a lot to Northland. They helped me on my way. It was pretty tough telling them I was leaving. But they were great. They could understand why I was leaving, and how I had to look after myself."
He said it was not too cold in Dunedin, and he was bringing his mother and daughter, Asema (3), south to live.
"It's going to just make it easier for me to get around."
Vainikolo's life has been a rags-to-riches story over the past two years.
After leaving Marcellin College, he played senior rugby for Auckland Marist and made the Auckland age group sides.
But a call from Adriaan Ferris early last year about playing for Northland club side Wellsford changed Vainikolo's rugby career.
He made a huge impact at Wellsford, scoring more than 35 tries in the season, which led to his winning a spot in the Northland side.
The Tongan-born flier scored five tries for the Cambridge Blues, good enough to win him a spot as a draft player in the Highlanders, picked seemingly out of nowhere by coach Glenn MooreHe played every game for the southern franchise, picking up six tries in a struggling side.
Hopefully, for Southern fans he will continue that form, and that black jersey may beckon.
Otago also announced yesterday it had re-signed lock Tom Donnelly until the end of the 2010 season.
Donnelly (26) has played 50 games for the province and 38 games for the Highlanders.
Donnelly was also called into the All Blacks' wider training squad at the start of the domestic test season this year.
Otago Rugby Football Union chief executive Richard Reid said it was great to have a player with Donnelly's experience re-sign with Otago for two more years.
Otago coach Steve Martin said he was delighted Donnelly had decided to stay with Otago.
Donnelly was a senior player, an integral part of our leadership group and a valuable team member on and off the field.
