Watt announced the destination on Twitter, while Ian Rapoport of NFL Network confirmed the details.
Watt, 31, has spent his entire 10-year NFL career in Houston, becoming the greatest player in franchise history. He, Lawrence Taylor and Aaron Donald are the only three-time winners of the NFL's Defensive Player of the Year award.
The Texans and Watt mutually parted ways last month, further enflaming questions surrounding the future of the franchise. Houston has been engulfed in controversy the entire offseason after quarterback Deshaun Watson requested a trade.
While both sides remained professional during Watt's departure, his frustration with the franchise was clear toward the end of the season. Teams immediately began expressing interest as soon as he hit the market, with around a dozen teams reaching out, according to ESPN's Ed Werder.
Watt remains an effective player when he's on the field, although injuries ravaged the second half of his Texans tenure and made him a far less dominant pass-rusher. Watt has missed 32 games over the past five seasons and set a full-season career low with five sacks in 2020.
Pro Football Focus nevertheless gave Watt an excellent overall grade of 85.4 for the season, owing in large part to his continued dominance against the run.
Adding a player of Watt's caliber is an obvious boost for a Cardinals team looking to make a Super Bowl push.
Arizona ranked 10th in Defensive DVOA last season, but Watt could be the potential missing piece in its front seven. Watt will be reuniting with wideout DeAndre Hopkins, whom the Texans traded to the Cardinals last offseason.