[2] His uncle is the former Labour Party leader Ruairi Quinn.

Quinn was an unsuccessful candidate for Dáil Éireann in the Dún Laoghaire constituency at the 2007 general election.

[4] He was re-elected in June 2009 for the Pembroke-Rathmines electoral area, and was elected Lord Mayor of Dublin in 2013.

[5][6] In 2013, called for the direct election of Dublin's mayor, saying that direct election is a necessity if Dublin wants to compete with other similarly sized cities across Europe.

[9] He was nominated to the High Court in June 2023 and appointed in July 2023.