Yvonne Costello is a well-recognised practitioner in mergers and acquisitions, having gained a wealth of experience working for a multinational professional services firm.

She is a dual-qualified solicitor in England and Wales and Ireland, and is an associate of the Irish Taxation Institute.


Prior to joining Armstrong Teasdale, Yvonne was a corporate law partner at Kerman & Co. in London. She joined Armstrong Teasdale in early 2021 when the firms combined. Before that, she worked as a solicitor for a law firm in Dublin. Yvonne also has past experience working for a multinational professional services firm that specialises in accounting, tax and consulting.


  • Law Society of England and Wales  (2009)
    • Law
  • Irish Tax Institute  (2006)
    • Taxation
  • Law Society of Ireland  (2006)
    • Law
  • University College Dublin  (B.C.L., 2001)


  • England and Wales, 2009
  • Republic of Ireland, 2003

Professional Activities

  • Tax Institute of Ireland (Member)
  • Law Society of Ireland (Member)
  • Law Society of England and Wales (Member)
  • Member of the Irish Lawyers in London group (Member)

Charitable and Civic Involvement

  • Global Girl Ambassador Partner Programme (Member)


  • The Best Lawyers in the United Kingdom®, Corporate Law (2023-present)
  • The Legal 500, Recommended Lawyer, Corporate and Commercial: M&A (2021)
Contact Us
  • Worldwide
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  • Orange County, CA
  • Philadelphia, PA
  • Princeton, NJ
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  • St. Louis, MO
  • Washington, D.C.
  • Wilmington, DE
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Royal College of Surgeons of England
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Wilmington, DE
1007 North Market Street
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