The Welsh international will join Wales defence coach Shaun Edwards at the London club ahead of the new Aviva Premiership season.
Powell, 28, who has been capped 14 times for his country and represented the British and Irish Lions in South Africa last year, fell out of favour at Cardiff after suffering what was described by the club as Ã¢â‚¬Å“losing his way.”
Powell received a 15-month driving ban after an incident with a golf buggy following the Six Nations victory over Scotland.
There is no doubt that the move was made more appealing by EdwardsÃ¢â‚¬â„¢ role at the club, but Powell is also keen to work with head coach Tony Hanks.
Ã¢â‚¬Å“All I want to do now is get my head down, improve as a player and hopefully if selected, play in the World Cup next year for my country,” said the back row forward.
Ã¢â‚¬Å“I think with the coaching team and setup here at Wasps, I will have the perfect opportunity to do that.
“I know Shaun Edwards well of course from my time with the Welsh team, and I took little persuading once I met with Tony Hanks and Trevor Woodman about how serious this team is about success and winning.”
Hanks echoed the sentiment saying: “Andy makes his move from Cardiff based on his desire to drive both his club and international career and while his rugby ability is obvious.
“The Wasps coaching team have all warmed to Andy immediately and are impressed by his drive and enthusiasm to relocate to London and join Wasps.”
Wasps have seen a number of high profile players leave the club in the off-season, most notably Danny Cipriani to Melbourne Reds and Paul Sackey joining Jonny Wilkinson at French side Toulon.
The signing of Powell, as well as the retention of Riki FluteyÃ¢â‚¬â„¢s services for another year, will undoubtedly strengthen the side ahead of the new campaign, which includes their return to the Heineken Cup.
Wasps’ campaign begins against Harlequins as part of the double header at Twickenham.
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