The 21-year-old has signed a four-year deal after passing a medical for an undisclosed amount, though reports claim that it is for a £9m fee that means Cardiff have broken their transfer record for the second time this summer.
The Bluebirds broke their transfer record just a few weeks ago with the £8.5m capture of Andreas Cornelius from FC Copenhagen.
There had been reported interest in the promising England U21 centre-back from numerous clubs over the summer with both Manchester City and Liverpool said to be monitoring the situation but Malky Mackay followed up their initial interest with a cash bid.
“First and foremost I want to say how happy I am to have signed with Cardiff City Football Club. I’m delighted to be here and excited for this fresh challenge," said Caulker.
“I spoke to the Gaffer yesterday, liked what he had to say and am excited about the plans he has for the Football Club.
"You get the sense of excitement from everybody at the Club in the build-up to the season’s kick-off at West Ham and I’m really looking forward to being part of it.
“I thank Tottenham for everything they’ve done for me, having been there since I was a kid. But I’m here to back myself up now and show what I can do. This is a fresh start, a new chapter and I’m here to kick on.”
Caulker, who came through the academy at Tottenham, is the Bluebirds' fourth signing of the summer following their promotion to the Premier League.