The 22-year old has signed a four-year deal with the R's, departing the relegated Cardiff City after just one season, and looking forward to playing under ex-Tottenham boss Harry Redknapp at Loftus Road.
The former Spurs youngster was also thrilled to get the chance to form a strong partnership with ex-Manchester United star Ferdinand.
"I'm very excited to be here. It was important for me to be back playing in the Premier League and Harry Redknapp has given me the opportunity to be at this fantastic club," Caulker told the club's official website.
"Harry was a big factor for me having worked with him at Tottenham. He was very keen for me to join and it was a big plus knowing the manager wants you.
"Being able to play with Rio was also a big draw. He has been a role model of mine for many years, along with Ledley King.
"To have the opportunity to play alongside him (Ferdinand) was something I felt I couldn't miss out on."
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