Born and raised in Birmingham, England, Carsley represented the Republic of Ireland at international level and was chosen for the 2002 FIFA World Cup.

[3] A defensive midfielder, Carsley began his career with First Division club Derby County and made his debut in a 6–1 Anglo-Italian Cup group stage victory over Cesena on 6 September 1994.

[4] He went on to become a regular fixture in the team during the 1994–95 and 1995–96 seasons, making 37 appearances and scoring two goals in the latter campaign to help the Rams to a second-place finish and promotion to the Premiership.

[9] In the second-tier, Carsley was encouraged to play a more advanced midfield role by manager Brian Kidd and showed the best goalscoring form of his career,[10] topping the club's chart with 11 goals,[11] though Rovers could finish no better than 11th.

[12] Despite falling out of favour with new manager Graeme Souness and handing in a transfer request, Carsley played on into the 2000–01 season, before leaving the club in December 2000.

[10] Carsley signed with struggling Premiership club Coventry City in December 2000 on a four-and-a-half-year contract for a fee believed to be £2.5 million.

[14] Despite Coventry looking outside bets for a place in the promotion playoffs,[15] Carsley left the club in March 2002, having made 52 appearances and scoring four goals.

[24] He returned to the team for Everton's FA Cup fourth round replay versus Chelsea on 8 February 2006, replacing Leon Osman late in the 4–1 defeat.

[28] Carsley turned down the offer of a new contract and departed Goodison Park at the end of the season,[29] after making 199 appearances and scoring 13 goals during just over six years with Everton.

[41] He made his international debut at U21 level in a 3–1 1996 European U21 Championship qualifying defeat to Portugal U21 on 14 November 1995 and represented the B team in a match against the League of Ireland XI 18 months later.

[2] Carsley won his first cap at senior level in a 1–1 1998 World Cup qualifying draw with Romania on 11 October 1997 and played in Ireland's two playoff matches, which were lost 3–2 on aggregate to Belgium.

[43] On 7 April 2004, Carsley declared that he would take a break from international football in order to focus on his family and winning his place back in the Everton team.

[57] He had a successful 2016–17 season, managing the team to a top place finish in the North Division of the Professional U18 Development League 1 and to the 2017 FA Youth Cup Final.

[60] Later that season, Carsley took sole caretaker charge when Robins left the club on 14 February 2013,[61] until Steven Pressley's appointment on 8 March.

[68] With incoming head coach Dean Smith watching from the stands, Carsley's tenure ended with a 1–1 draw away to Bolton Wanderers on 30 November.

[77] On 9 August 2024, Carsley was appointed interim head coach of England national football team after Gareth Southgate departed the role.

[78] He said "As I am very familiar with the players and the cycle of international football, it makes sense for me to guide the team while the FA continues the process to recruit a new manager".

[10] His elder son Callum became a footballer, playing as a defender for Reading United, and as of 2024 is the assistant technical director at Birmingham City.