Born in Waterford, O'Shea joined Manchester United when he was 17. He spent loan spells at Bournemouth and Royal Antwerp before establishing himself in the Manchester United first team, going on to make 393 appearances and scoring 15 times in all competitions across 12 seasons. O'Shea won 14 trophies at United; five Premier League titles, one FA Cup, two Football League Cups, four FA Community Shields, the UEFA Champions League and the FIFA Club World Cup. He is one of the most decorated Irish footballers of all time, with only Denis Irwin, Roy Keane, Steve Heighway and Ronnie Whelan having accrued more honours. He joined Sunderland in July 2011. Having played 256 times for the Wearside club and scoring four goals, he signed for Championship side Reading in July 2018 until his retirement in May 2019.