"I still have business to take care of with Wigan but I'm over the moon knowing I'll be with the Warriors for the next three years," he said. "I was thrilled to meet up with [owner] Eric Watson and the club has been terrific throughout.
"They flew Mum out to New Zealand so they could show her around and she was absolutely blown away by what Auckland had to offer.
"I was in New Zealand with England for the Four Nations in 2010 and loved what I saw then."
Tomkins said the key for him was taking another step up in his career by challenging himself in the NRL.
"I'm really grateful to Wigan for helping to make this possible by giving me an early release. I love the club and the people here and always will, but this is the next big step for me."
The signing of Tomkins, who is likely to earn in the region of $700,000 a year, makes the future of Kevin Locke at the club uncertain. Locke could find a place in the halves or on the wing and has also been linked with the Canterbury Bulldogs.
For Watson, Tomkins' signing is one of the most significant since he took over the club in late 2000.
"Sam is unquestionably among the biggest names in the game today, certainly the biggest in England," he said.
Coach Matthew Elliott pointed to the Burgess brothers at South Sydney as well as the Bulldogs' James Graham as examples of players moving from the United Kingdom to make their mark in the competition.
Wigan owner and chairman Ian Lenagan said Tomkins, who has scored 21 tries in 20 tests, would leave Wigan with the club's full support.
"We have a principle of developing players to enable them to take up opportunities at the highest level, like playing in the NRL," he said.
"We're disappointed to see Sam going but we want to give him this opportunity."
Warriors chief executive Wayne Scurrah said both clubs planned to combine again. Wigan general manager Kris Radlinski spent time at the Warriors recently while Warriors assistant coach Ricky Henry visited Wigan in July. Scurrah and Warriors general manager of football operations Dean Bell also visited Wigan earlier this season.
Captain Simon Mannering was named Warriors Player of the Year for a record third time at the annual awards dinner last night.
Mannering, who won the award in 2008 and 2011, missed the event because his partner was in labour with the couple's first child.
Manu Vatuvei was named Clubman of the Year and Ngani Laumape was Rookie of the Year.
- Herald staff
