Power coach Ken Hinkley flagged his desire to lure the 26-year-old to Alberton earlier in the week and the fifth pick at the 2006 NAB AFL Pre-season Draft wasted no time in signing with the club.
White played 105 games for the Tigers, including 16 games this year, but was often forced to start as the side's substitute for the 2013 season.
He fielded offers from several rival clubs, but White said he chose to join the Power for the opportunity of a starting 22 position.
“It’s a massive opportunity to come to a great club in Port Adelaide, and I’m really looking forward to what the next few years can bring the club and me personally,” White told Port Adelaide's website.
“It’s a massive thing for me to come over to SA and into a group that’s played in two finals this year.
“I know Ken runs a pretty tight ship and I’m really excited about the challenge of trying to slot into the 22 each week and hopefully be playing finals come the end of next year.
“Ken and Alan Richardson have outlined some key roles for me to play throughout the year, but I’m just looking forward to getting out there and playing on some quality opponents, as well as hopefully winning a lot of games.”
As well as the obvious need from a football perspective, Hinkley has previously spoken about the importance of bringing the "right" sort of characters into the club.
He said White ticked both boxes.
“Matt has got great character and is a fantastic person – he’s exactly the type of player we want to be getting to our football club,” Hinkley said.
“Attracting the right type of people to our club is so important.
“But he also satisfies our list needs and we believe he can play a couple of roles for us over the next three years.
“Getting some outside run to the club was a priority going into this trade period and it is a tremendous result that we’ve been able to secure a player of Matt’s quality so early in this period.”