[1] He studied Legal Science at Trinity College Dublin, graduating in 1982,[2][3] and trained to become a barrister at the King's Inns.
[3][5][6] Jim Mansfield, Dunnes Stores, Quinn Group, the owners of the Shelbourne Hotel, Treasury Holdings, Comcast, Allied Irish Banks, and Declan Ganley were among his clients.
[18][19] The precipitation of the post-2008 Irish banking crisis led to many court disputes, with O'Moore appearing in many, including on matters of insolvency law and in cases on behalf of the National Asset Management Agency.
[23] He also acted for the Sisk Group and Seán Quinn and his family in defending actions taken by Anglo Irish Bank.
[34] He was appointed the lead counsel for a Central Bank of Ireland inquiry into Irish Nationwide Building Society in 2017.