Campbell has moved to Selhurst Park for an undisclosed fee after he agreed terms on a three-year contract with Palace.
The 26-year-old, who came through the youth ranks at Manchester United, has been capped by England once in 2012.
While on United’s books, Campbell had loan spells with Antwerp in Belgium, Hull City and Tottenham.
He then spent three-and-a-half years at Sunderland before arriving at Cardiff in January 2013 for around £650,000.
He's not a bad player but I'd have thought he'd have filled out a bit and put on some muscles by now- shea666