The Brazilian defender will spend the entire 2012/13 season at Loftus Road, and he admits the move is crucial for the next stage of his career.
"I'm so happy to be here," Fabio told QPR's official website. "This loan is so important for me in terms of my career. I want to play as many games as possible here. I want to play well and win games as well.
"It's a good move for my career and for my confidence. Sir Alex Ferguson said that I'd enjoy it here and told me to play as many games as I can. I know that QPR is a club with great history. I read about the history and that's why I'm here.
"I also came here because I'm ambitious. I want to help QPR progress up the Premier League. Hopefully the fans will enjoy watching me in action, because I'll do my best."
QPR manager Mark Hughes feels the deal benefits all parties involved, as his side gain a talented player who will hone his craft before returning to Old Trafford.
"It's a great opportunity for us to loan a good, young player, who has decent experience of playing for a top club like Manchester United," said the former Reds striker.
"He's played a lot of senior games for United, so it shows the quality he's got. I know they think very highly of him and we believe he has all the attributes to be a success here next season.
"We can give him the games he's craving at this stage of his career, so it benefits everybody. He's very versatile - he can play left or right-back and he's also been utilised in midfield by Sir Alex in the past, so we know what we're getting, and