Nelsen will move to Loftus Road on July 1 following the conclusion of his contract at Tottenham. The New Zealander, 34, joined Spurs in January after seven years at Blackburn where he played under Rangers boss Mark Hughes.
"I am really pleased to be joining QPR," Nelsen told www.qpr.co.uk. "I have obviously got a lot of history with the manager and that was a massive draw for me."
He added: "I like his winning attitude. He and all his staff just have an absolute desire to win, and that's what the Premier League is all about.
"If you haven't got that, you won't be successful.
"The owners have got fantastic ambition and it's exciting to become a part of that. There's a real buzz about the place and it is a privilege to be here."
Hughes said: "I am delighted to bring Ryan to the club. I know what he is all about and what he can offer us, both on and off the pitch.
"He hasn't played a lot of football in the past year or so but he is fit, raring to go, and looking forward to representing his country at the Olympics.
"Ryan has got great experience in the Premier League and that is something our squad is lacking a little bit at present.
"He's a fantastic professional with a great work ethic and it will benefit the younger lads in the group to see how he goes about his work."
Source: PA
Source: PA