McClaren, who has also managed Middlesbrough, FC Twente, Wolfsburg and Nottingham Forest, has been out of the game since his second spell with Twente ended in February.
He has recently been linked with the England Under-21 post following the Football Association's decision not to offer a new contract to Stuart Pearce. But now he will form part of Redknapp's backroom team as QPR try to secure an immediate return to the Barclays Premier League.
Redknapp, who already has a vastly experienced coaching set-up that includes the likes of Kevin Bond, Joe Jordan and Steve Cotterill, will be hoping McClaren can add something different to the group and was pleased to recruit the 52-year-old.
"I am delighted to have been able to bring Steve in," he said.
"Everyone in the game knows what a top coach he is and he'll add something different to the group, regardless of how long he is with us for. This is a very important season for us and I wanted to look at freshening up the whole place, not just the playing side.
"I want new ideas, different opinions and another experienced head to speak to. That's what Steve brings. Along with Kevin (Bond) and Joe (Jordan) I've got a brilliant backroom team and their input is going to be so important for me this season. Steve adds to the excellent staff I already have here."
Many may view the move as a surprise given McClaren's managerial experience but a return to coaching is something he is relishing.
"I'm delighted to take up this position offered to me by Harry and QPR," he said.
"Whilst it still remains my ambition to manage again this gives me an ideal opportunity to stay involved and work on the field with one of the top managers in this country and a very ambitious club. Rest assured, I'll be doing all I can for Harry, the club and the fans to help QPR return to the Premier League."