The defender made 250 appearances for the Cottagers but was released by Rene Meulensteen and moves to Loftus Road in a bid to bring Harry Redknapp's side up to the Premier League.
Hughes made 250 appearances for Fulham and was part of the side that drew 1-1 at Sheffield United in the FA Cup fourth round last weekend.
The Northern Ireland international defender has dropped down to the Championship to join Harry Redknapp's promotion hopefuls and is relishing the chance to work under the former Tottenham boss.
"The opportunity to come here was too good to turn down," said the 34-year-old, who moved to Fulham from Aston Villa in 2007. "Harry tried to sign me as a youngster when he was at West Ham, so it's nice that I've now got the opportunity to play for him.
"QPR are a club looking to get back into the Premier League and if I can come in and help in some small way, I'll do my best to do that."
Redknapp told the club's official website: "Aaron is a very experienced player and with the injuries we've suffered lately, he's a fantastic addition."
The club has also confirmed the signing of 21-year-old Brazilian striker Dellatorre on loan from Desportivo Brasil.
"He's a young player from Brazil, who our scouts have watched and like," Redknapp said. "I've not been to Brazil to see him play, but he's appeared on the radar and is a young player who is probably one for the future rather than the here and now."