An Irish amateur international, Irwin began his career at Bangor before moving to Welsh side Cardiff City in 1971. Brought in to replace Frank Parsons, Irwin was thrown straight into the Cardiff side and performed admirably, including winning the 1971-1972 BBC save of the season award for a spectacular save during a 2-0 defeat in the FA Cup against Leeds United in February 1992. During the Welsh Cup final match during the 1972-73 season Irwin became the first Cardiff goalkeeper to be sent off during a match after receiving his marching orders against Bangor City. Irwin held the position of first choice goalkeeper for four seasons until the arrival of Ron Healey. He eventually left the club in 1978 and went to play for the Washington Diplomats in the NASL.
He went on to play at various teams in the NASL before finishing his career with two years playing indoor football in the Major Indoor Soccer League. After his retirement Irwin took up an assistant manager role at the University of Portland alongside former Cardiff teammate Clive Charles. During his time at the University he has an impressive record of training goalkeepers. The five starting goalkeepers who have trained under Irwin, Greg Maas, Kasey Keller, Stuart Dobson, Scott Hileman and most recently Curtis Spiteri, have all gone on to play professional football. Following the sudden death of Charles in 2003 Irwin was promoted to headcoach after serving as his assistant for sixteen years.
Irwin has been involved with goalkeeper coaching throughout the US women's teams and various youth levels of the men's team.
Irwin and his wife, Liz, live in Portland with their two sons Bryan, who plays for the university team, and Nicholas.