The 25-year-old, who completed his move from Sunderland when signing a three-and-a-half year contract on Monday, won promotion to the top flight while on a season-long loan at Hull in 2008 and gained his solitary England cap in a 3-2 friendly defeat to Holland in February 2012.
Campbell, for whom Malky Mackay's promotion-chasers paid an undisclosed fee, told the club's official website: "I'm delighted that this move has come off.
"I've not played much football this season so to get a fresh start at such an ambitious club as Cardiff is great for me. I can't wait to get back doing what I love here.
"When you switch clubs, it's important to know that you're going to a place that really wants you.
"Last time I was in the Championship we got promoted with Hull. That was brilliant and it's something I now want to do with Cardiff.
"The lads here have done fantastically well already this season and I'm coming in now to hopefully add to what they've achieved so far.
"The aim for us all is to get to the Premier League; when you get there, everyone is watching.
"I'd love to represent my country further and by performing week in week out in that division is how you do that.
"It's not on my agenda right now in all honesty though as we've got a lot of work left to do this season if we're to achieve our ambition of promotion in May."