Capaldi rejected a new contract with Plymouth and on 25 May 2007 he signed a three-year contract with Cardiff City, joining on a Bosman free transfer. He began the season as first-choice left back but after struggling to perform consistently found himself dropped from the side, being replaced by Chris Gunter. Following the sale of Gunter on 1 January, he returned to the first-team squad and began to settle more comfortably into the side, including playing in all six of the club's matches on their run to the 2008 FA Cup Final.