The 19-year-old has signed a five-year deal at Villa Park.
"He's dynamic, very quick and a maverick-type player - you never know what he's going to do next and I mean that as a compliment," Villa manager Tim Sherwood told BBC WM 95.6.
"He's a huge asset for this club. He can hurt the opposition and I'm delighted to bring him here."
Traore made four senior appearances for Barca but the majority of his football has been with the Spanish giants' B team, scoring eight times in 63 Segunda Division games. He has represented Spain at under-16, under-17 and under-19 levels.
"He comes from a very good academy with Barcelona and I've known him a long time," said Sherwood.
"He makes his mind up when he gets the ball and those players are rare - there aren't many players in the Premier League that can do that.
"We're getting him at the midway part of his development. He's not the finished article by a long way but he can certainly help us out in the short-term and in the future."
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Aston Villa have completed the signing of Barcelona winger Adama Traore for a fee reported to be around £7m.