Ms Mona Costelloe > ByrneWallace LLP > Dublin, Ireland > Lawyer Profile

ByrneWallace LLP
88 Harcourt Street
Saint Kevin's
DO2 DK18

Work Department

Litigation and Dispute Resolution


Partner, Litigation & Dispute Resolution


Mona Costelloe is a Partner in the ByrneWallace LLP Litigation & Dispute Resolution team. She advises a wide range of national and international clients on complex litigation issues, including financial services litigation, administrative law and contentious regulatory matters, contentious procurement, judicial reviews, EU law challenges, property disputes and contentious construction disputes, product liability and sale of goods claims.


  • Dublin Solicitors Bar Association
  • Law Society of Ireland
  • Association of Regulatory and Disciplinary Lawyers
  • Commercial Litigation Association of Ireland


  • Masters of Law (LL.M) Trinity College Dublin, 2000
  • BA, Law and European Studies, University of Limerick, 1999

Lawyer Rankings

Ireland > Dispute resolution

ByrneWallace LLP remains best known for contentious matters involving public sector bodies, including those in the health, education and tourism sectors. Jon Legorburu leads the team and has an impressive history in commercial litigation and public sector disputes. Mona Costelloe is another senior name with extensive expertise in real estate disputes, regulatory enforcement matters and more general commercial litigation. Sean O’Donnell is also noted for contentious regulatory work, and Mark O’Shaughnessy is a growing force in the market. Valerie Hourigan is rated for real estate and procurement disputes.