Mick O’Reilly was born in the Coombe in October 1946 and raised in Ballyfermot. He left primary school early, following an altercation with a Christian Brother. He worked at Sherling’s, May Robert’s, and Lincoln & Nolan’s car factory from a young age before pursuing trade unionism.

O’Reilly first joined the Communist Party in Britain, where he lived for two years before joining the Irish Party in 1967. He joined the Labour Party in 1989. In 1992, O’Reilly became District Secretary and sat on the committee for the Irish Congress of Trade Unions. Four years later, he relocated to Belfast as the first ever nationalist Regional Secretary.