The 21-year-old has failed to establish himself in the first team at Old Trafford, and will now hope to revive his career in west London under the management of Mark Hughes
The Brazilian left-back will spend the 2012-13 campaign at Loftus Road, where he will work under former Reds striker Mark Hughes.
Speaking to his new club's official website, Fabio said: "I'm so happy to be here. 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 was also delighted with the arrangement, as he feels his side have snapped up a talented player who will earn valuable experience 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 Hughes.
"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.
The news comes after his twin brother Rafael penned a new four-year deal with the Red Devils.