Steven Caulker has signed for Barclays Premier League newcomers QPR, their owner Tony Fernandes has announced on Twitter.
The 22-year-old centre-back has joined Harry Redknapp's side after just one season at Cardiff, who were relegated from the Premier League at the end of the 2013-14 season.
Fernandes said: "I would like to announce the signing of Stephen Caulker to Queen's Park Rangers. Welcome."
Caulker has signed a four-year deal after an undisclosed fee was agreed with Cardiff for a player who won his solitary England cap in 2012.
The former Tottenham defender completes his move to Loftus Road just days after fellow centre-back Rio Ferdinand also agreed to join the newly-promoted Barclays Premier League club.
"I'm very excited to be here. It was important for me to be back playing in the Premier League and (QPR manager) Harry Redknapp has given me the opportunity to be at this fantastic club," Caulker told www.qpr.co.uk.
"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 was something I felt I couldn't miss out on.
"Our first aim this season has to be to get to 40 points to make sure we stay up. That's our first goal."
Caulker, an £8million signing from Tottenham for the 2013-14 season, played every minute of Cardiff's debut season in the Premier League that ended in relegation.
The London-born defender made his first Spurs appearance under Redknapp in 2010 and the Rangers boss is delighted the two have been reunited at Loftus Road.
"I know the ability Steven has and I think it's an important signing for the club - for the here and now, and for the future," Redknapp said.
"I had him at Tottenham and I was very surprised when they decided to let him go last summer because I thought he had a big future there.
"He's young and is already a fine player, but he has so much more potential. It's a really excellent signing for the club.
"When good players like Steven become available, who can come in and have a real impact, you've got to try and get them.
"I'm sure he will come in and show exactly what he's capable of. He's got everything to be a top, top centre-half, so I couldn't be more pleased to have him."