[1] He was confirmed as Dublin senior football team manager on 12 December 2019, succeeding Jim Gavin on a three-year contract.

Outside playing and coaching, Farrell served as chief executive and founder member of the Gaelic Players Association (GPA), the official representative body for inter-county footballers and hurlers.

[5] A talented minor footballer who reached an All-Ireland MFC final in 1988, Farrell was called onto the senior panel in 1990 but suffered a serious setback when he ruptured his cruciate knee ligament in a club game and missed Dublin's four-game series against Meath in 1991.

A detailed account of his playing career is recorded in his autobiography, which was released on 30 November 2005, the same night Farrell announced his official retirement from inter-county football.

In November 2000, the GPA's first annual general meeting took place in Killarney, County Kerry, where Farrell was elected as chairman.

Appointed CEO in 2003, Farrell oversaw the rapid growth of the organisation and helped negotiate Government funding for players in 2007.

He later managed the Dublin minors to an All-Ireland MFC title, defeating Meath in the final at Croke Park in September 2012.

In farrell's second year in charge, Dublin won the 2014 All-Ireland Under-21 Football Championship, defeating Roscommon at O'Connor Park in Tullamore.

[10] Farrell also worked as a performance coach for the Dublin senior hurling team under the management of Mattie Kenny.

[11] On 1 April 2021, amid the COVID-19 pandemic in the Republic of Ireland, the Irish Independent published photographs of a coach-led group of Dublin team members, including All Stars Footballer of the Year Brian Fenton, whom it reported had gathered at Innisfails GAA club before 7am on the previous morning.

[23] He continued to play throughout his Dublin GAA career,[2][page needed] including for St Brendan's Phoenix Park hockey club.