Irwin is the joint most successful Irish footballer in history, a record he shares with Ronnie Whelan and fellow Manchester United stalwart Roy Keane, having won 19 trophies in his career.

[8] As a schoolboy, he excelled at both Gaelic football and hurling, and played at Croke Park more than once, on one occasion marking future teammate Niall Quinn.

[9] Irwin began his career with Leeds United in 1983, making 72 appearances in the Second Division, before moving on to Oldham Athletic on a free transfer in 1986.

[14] Irwin made his last appearance for Manchester United at Old Trafford against Charlton Athletic on the final day of the 2001–02 Premier League season (11 May 2002), which ended in a 0–0 draw.

He made his competitive international debut on 17 October 1990, when the national side began their UEFA Euro 1992 qualifying campaign with a 5–0 win over Turkey at Lansdowne Road.

His final international appearance came on 17 November 1999, at the age of 34, when Republic of Ireland lost to Turkey in the UEFA Euro 2000 qualifying play-off second leg in Bursa.

He was then suspended for Republic of Ireland's final group game (0–0 draw vs. Norway) and was an unused substitute in the 2–0 loss to the Netherlands in the Round of 16.