The 28-year-old was recalled from a loan spell at Standard Liege earlier this month after making 11 appearances for the Belgium side.
Hayden will now spend the remainder of the campaign at Loftus Road after becoming QPR's second signing of the winter transfer window following the arrival of forward Michael Frey from Royal Antwerp.
"I feel very happy, very pleased to be joining QPR," Hayden told the club's official website. "I am just delighted to get it over the line.
"It is obvious to see the position the club are in at the moment but it is a challenge that I feel I can add some value to, on and off the pitch - be an experienced player and be a leader to try and help the club stay in the league.
"Everyone knows what the Championship is like but if we can get a consistent run of performances, hopefully the points will come."
The Arsenal academy product has plenty of experience of playing in the second tier, having made 65 Championship appearances across spells with Newcastle, Hull City and Norwich City.
QPR are currently languishing in the drop zone and three points from safety, but Hayden is seemingly ready to join the club's fight to retain their Championship status.
Hayden added: "You can take the easy option in life and do things the easy way or you can take a challenge on and go head first into it.
"That's what I wanted to do here. I have looked at the squad and there are some really good players in it. There is definitely enough there but it is about us proving that on a matchday when it counts."
The defensive midfielder could make his debut for Marti Cifuentes' side in Saturday's clash with Blackburn Rovers Ewood Park.