Sarah O’Sullivan is an Associate at Brinen & Associates and co-leads the firm’s Corporate Department. Based in Dublin, Ms. O’Sullivan is instrumental in expanding the firm’s international practice and serves as a key liaison for cross-border matters between the United States and Ireland.

Sarah advises corporate clients across a range of industries, providing practical, strategic guidance on business formation, corporate governance, transactions, and tax sensitive structuring. Sarah also supports the firm’s litigation team in complex commercial disputes, arbitration, and mediation proceedings.

Ms. O’Sullivan joined Brinen & Associates in 2021 after completing her LL.B. at the University of Limerick, Ireland and the Law Society of Ireland’s FE-1 entrance examinations. Sarah is admitted to the New York bar and is completing her qualifications for admission as a Solicitor in Ireland. 

Sarah’s approach combines a broad understanding of corporate and commercial law with a solutions-first mindset. She is known for her clarity, responsiveness, and ability to bridge legal and business goals across jurisdictions. 

Representative Experience includes:

• Advising on U.S. company formation, structuring, and cross-border expansion
• Drafting operating agreements, shareholder agreements, and key corporate governance documents
• Supporting domestic and international Mergers &Acquisitions transactions, including due diligence, and closing coordination 
• Providing corporate counsel to startups and closely held businesses on day-to-day legal matters
• Preparing contractor and employment agreements, Non-Disclosure Agreements, and internal compliance documents
• Assisting with arbitration, mediation, and trial preparation in complex commercial disputes
• Securities filings, such as Form 8-K, and securities offerings under Securities Act of 1933, including Form S-1, Form S-3, and related prospectuses.