The 21-year-old spent time on loan with Serie A outfit Juventus last season and has made just one Barclays Premier League appearance for the Gunners in the last 15 months, in Sunday's 8-2 defeat to Manchester United. Traore becomes the third Loftus Road signing made under new owner Tony Fernandes, following Joey Barton and Luke Young.
"When I talked to Neil Warnock he was very passionate about what I could bring to the club," the Frenchman told the club's official website, www.qpr.co.uk.
"He was very motivated about playing me week in, week out, and that's what I need at this stage of my career.
"I've not been able to prove and show what I'm all about because I've been at two big, big clubs like Juventus and Arsenal. I'm looking forward to coming here and playing regular football. The ambition of the new owners and the calibre of players they are signing is something that really attracted me to the club."
Traore will wear the number 13 jersey at the west London club and manager Neil Warnock was delighted to secure his signature.
"Armand has been my number one defensive target for a while now," he said. "I've been speaking to Arsene (Wenger) for a couple of weeks.
"He's a young and exciting lad who I think can only get better playing for a side like ourselves on a regular basis. He needs games and he'll get that here.
"Nobody has seen the best of him yet, but over the next couple of years I'm confident he'll show the quality that I clearly believe he has.
"He'll be a great outlet for us down that left hand side. He's got all the attributes you need to be a top, top defender."
Source: PA
Source: PA