Seamus McDonagh was born 6 October 1952 in Rotherham to an Irish family.
His playing career as a top class goalkeeper saw him won 25 caps for Ireland and accumulate more than 400 appearances in the English leagues.
After his playing career he moved into coaching, initially as player-manager with Galway United, before he became a goalkeeping coach.
McDonagh's started at Rotherham United, and he spent a month on loan at Manchester United in 1973, before joining Bolton Wanderers. He was ever present as Bolton secured the Second Division title in 1977–78 and he set a club record of conceding only 33 goals in a 42-match season.
Everton then moved to sign McDonagh for £250,000 when Bolton were relegated in 1979–80 but within a year he had returned to Bolton. He moved on to Notts County for two seasons before he embarked on loan spells at Birmingham City, Gillingham and Sunderland.
He spent two years in US indoor soccer with Wichita Wings in 1985 and 1987 then joined Scarborough. He had a loan spell at Huddersfield Town and a brief stint with Charlton Athletic before taking the player-manager's position with Galway United in 1988.
After his spell with the Tribesmen he had loan spells at Spalding United, Grantham Town (twice), Telford United and Arnold Town. He retired from playing in 1994.
McDonagh had coaching positions at several clubs including Coventry City, Mansfield Town, Nottingham Forest, Millwall, Rotherham United, Leicester City, Aston Villa, Plymouth Argyle and Hull City. He was appointed Sunderland's first-team goalkeeping coach by Martin O'Neill in December 2011 and O'Neill appointed him to the same role with Ireland in November 2013.