Matt is a highly skilled litigator with over 30 years of trial and appellate experience and serves as Co-Chair of the firm's Disciplinary Board Representation Practice Group. His practice is concentrated on the defense of lawyers against malpractice actions, Judiciary Law 487 claims and grievances. He also defends other professionals and handles general litigation matters on behalf of corporate clients. He has successfully tried cases in New York City and its surrounding counties and has secured dozens of victories in attorney liability cases in New York State’s appellate courts.
With a career-long focus on professional liability litigation, Matt lectures throughout the state on legal malpractice prevention and defense, ethics and professional responsibility. His articles relating to attorney ethics have been cited in the authoritative codification of the laws of New York, as well as New York’s leading treatise on the Rules of Professional Conduct.
Among his numerous professional memberships, he is President of the Theodore Roosevelt American Inn of Court and is a member of the New York State Bar Association's Law Practice Management and Insurance Committees. He is a longtime member of the Nassau County Bar Association and served as Chair of the Association’s Ethics Committee from 2019 to 2022. He is also a longtime member of the American Bar Association.
Matt has been recognized annually as a New York Metro Area Super Lawyer for over a decade and is rated AV Preeminent by Martindale-Hubbell, the highest peer-review ranking for an attorney's professional and ethical competence. A graduate of St. John's University School of Law and Fordham University, he is admitted to practice before the courts of the State of New York, the United States District Courts for the Southern and Eastern Districts of New York and the United States Court of Appeals for the Second Circuit.
Honors & awards
AV Preeminent by Martindale-Hubbell
New York Metro Area Super Lawyer
2012-2025
Year joined
2024
Results
Dismissal Secured in New York Legal Malpractice Matter
Lawyers' Professional Liability
October 22, 2024
We secured a decision granting our motion to dismiss an attorney malpractice matter in Orange County, NY. The plaintiff and daughter of the co-defendants sued her parents and our client for breach of contract, breach of fiduciary duty denominated as promissory estoppel, and constructive trust and sought damages of $800,000. The co-defendants allegedly purchased a property for the plaintiff to live and work in and agreed to deed the property to the plaintiff once she paid the mortgage in full.
Thought Leadership
Marshall Dennehey Announces 2025 New York Metro Super Lawyers and Rising Stars
October 30, 2025
Five attorneys from Marshall Dennehey’s New York City and Long Island offices have been selected to the 2025 edition of New York Metro Super Lawyers magazine.
California Initiates Automatic Expungement of Attorney Disciplinary Records
New York
Long Island, NY - Melville
Disciplinary Board Representation
February 1, 2025
In a first-of-its-kind move, the California State Bar endorsed a plan to expunge attorney discipline records-other than disbarment-after eight years. Legal Update for Lawyers’ Professional Liability - February 2025 is prepared by Marshall Dennehey to provide information on recent legal developments
Legal Updates for Lawyers’ Professional Liability - CASE LAW UPDATE
New York
Long Island, NY - Melville
Lawyers' Professional Liability
November 1, 2024
In an important decision issued earlier this year, the New York State Court of Appeals affirmed the dismissal of a Judiciary Law 487 claim against an attorney but removed an available defense for attorneys subject to subject to such clai Legal Updates for Lawyers’ Professional Liability - November 2024 is prepared by Marshall Dennehey to provide information on recent legal developments
Marshall Dennehey Announces 2024 New York Metro Super Lawyers and Rising Stars
October 24, 2024
Five attorneys from Marshall Dennehey’s New York City and Long Island offices have been selected to the 2024 edition of New York Metro Super Lawyers magazine.
Veteran Litigator Matthew K. Flanagan Joins Marshall Dennehey in New York as Shareholder and Co-Chair of the Disciplinary Board Representation Practice Group
Disciplinary Board Representation
Lawyers' Professional Liability
Miscellaneous Professional Liability
August 7, 2024
Veteran litigator Matthew K.
Classes and Seminars Taught
Attorney Discipline, Theodore Roosevelt American Inn of Court (with program chairs Hon. Randall Eng, Appellate Division, Second Department (ret.), and Hon. Helen Voutsinas, Appellate Division, Second Department), November 15, 2023
Risk Management and the Rules of Professional Conduct, Nassau County Bar Association, May 12, 2022
Cybersecurity: Are You and Your Firm Compliant: A Checklist for Lawyers, Joint Presentation of Nassau County Women’s Bar Association and Nassau County Bar Association Ethics Committee, March 3, 2020
Navigating Malpractice and Ethical Concerns for Trusts and Estates Attorneys, St. John’s University School of Law Continuing Legal Education Weekend, February 8, 2020
Legal Malpractice: Elements & How to Avoid It, Suffolk Academy of Law, December 12, 2019
Legal Malpractice: Reducing Your Risk and Strengthening Your Defense, St. John’s University School of Law Spring Continuing Legal Education Weekend, February 10, 2018
Lawyers’ Ethics: Escrow Accounts (with Hon. Leonard Austin, Appellate Division, Second Department), Theodore Roosevelt American Inn of Court, December 12, 2017
Judicial Ethics, What’s a Judge to Do? (with Hon. Vito DeStefano and Hon. Randy Sue Marber, Supreme Court, Nassau County), Theodore Roosevelt American Inn of Court, April 27, 2017
Legal Malpractice: Professional Liability Claims, Litigation Strategies and Attorney Discipline Procedures, New York State Bar Association, Melville, New York, March 31, 2017
Attorney Ethics: A Discussion of the New Statewide Procedures for Attorney Discipline Matters (with Abraham Krieger, Chairman of Grievance Committee for 10th Judicial District), St. John’s University School of Law Continuing Legal Education Weekend, February 25, 2017
Legal Malpractice Update, Nassau County Bar Association, February 1, 2017
