Kiely moved to Charlton Athletic for a fee of £1 million on 26 May 1999 and made his debut on 7 August against Barnsley. He was Charlton's regular keeper from 1999 to 2005, and was popular with the club's fans as well as having a majestic "shut out" rate. Having been signed from a lower-division club he was seen as an example of Alan Curbishley's ability to spot talent in unheralded players. Kiely made a point-blank save from Birmingham City player Christophe Dugarry in a game at St Andrew's on 3 November 2003; Charlton went on to win the game 2–1 and Kiely later named the save as the favourite one of his career. He also saved a penalty from Crystal Palace's Andy Johnson to help secure a 1–0 win in December 2004.