The 31-year-old has penned a two-and-a-half-year deal to join the rugby league outfit from Sale Sharks.
Powell made his Wales debut with a barnstorming display against South Africa in 2008. He went on to win 23-caps but has not featured for his country since last season's RBS 6 Nations.
"I had interest years ago in doing it," said Powell.
"I've achieved a lot in rugby union and I think it's something that I need to do now,
"Wigan are such a big club and it's come at the right moment
"They've been really good to me and they'll help me with the technical side of the game, but because of the way I carry the ball and tackle, I think it will suit me ideally.
"There were a few other league clubs that were interested, in Super League and the NRL, but Wigan was the one that I couldn't really turn down."
Powell has been signed as a direct replacement for Lee Mossop and Wigan chairman Ian Lenagan reckons he has all the attributes to cross-codes.
"We believe we have the perfect replacement for Lee in Andy Powell," added Lenagan.
"We are delighted that Andy is taking up the challenge in exactly the same that that Scott Quinnell did in the past. We think Andy Powell is exactly right for rugby league."
If Powell goes on to represent Wales in rugby league he will become the 100th player to do so in both codes.