Both players will remain until the end of the season. Chimbonda has already been released by Rovers whilst Routledge is a loan arrangement.
"I had to bring someone in to give Bradley Orr and Clint Hill competition.
To get someone of Pascal's experience and quality at this stage of the season is a massive boost."
Regarding Routledge, he added: "I think Wayne just needs an arm around him. He is a super lad and a super player.
"He has always had a soft spot for QPR and I am delighted to bring him back to the club.
"He hasn't done much training this week so we will have a look at him on Saturday and make a decision with regards to Sunday's game against Coventry."
Both players are delighted to join the Hoops for their promotion push.
Chimbonda said: "This is a good opportunity for me to be re-born as a footballer. Neil Warnock has given me a chance here and hopefully I can help QPR win promotion to the Premier League.
"I want to play good football here and enjoy myself on the pitch.
"The style of football that QPR play suits me, and this will provide a good challenge for me.
"I had a good talk with the manager, and he told me he wants me to come here and give my best. He is a manager who likes to win, and I am the same.
"I always give my best and that is what I will do here at QPR. I will do my best to win and I hope the fans will like me."
Routledge added: "I'm really pleased to be back here.
"QPR have made a great start to the season and I'm really looking forward to playing some games and helping the club push on during the remainder of the season."