Atty. Thomas P. O'Brien
Thomas P. O’Brien, Co-Chair of the White Collar Defense & Special Investigations Practice, advises clients throughout all phases of government investigations and prosecutions encompassing a broad scope of situations such as corporate compliance matters, fraud, and state and federal False Claims Act cases.
Profile Summary
About Thomas P. O'Brien at a glance
Thomas P. O'Brien is a Shareholder based in Los Angeles, California, practicing at Greenberg Traurig, LLP. They have 33+ years of legal experience, licensed to practice since 1993. Their practice focuses on white collar and litigation. Admitted to practice in California (1993). Educated at University of San Diego School of Law J.D. cum laude; Associate Editor, San Diego Law Review (—) and U.S. Naval Academy B.S. (—). Serands clients in Los Angeles, CA and the surrounding metropolitan area.
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About
- Thomas P. O’Brien, Co-Chair of the White Collar Defense & Special Investigations Practice, advises clients throughout all phases of government investigations and prosecutions encompassing a broad scope of situations such as corporate compliance matters, fraud, and state and federal False Claims Act cases
- He serves as both an advocate and counselor for corporations and individuals, guiding them from the start of government interactions to the end of trial proceedings
- Tom often carries out internal investigations for corporations and municipal governments with a strategic approach, aiming to prevent clients from potential legal violations or misconduct
- In the field of white collar defense, Tom manages cases of embezzlement, accounting fraud, and bribery, among others, addressing complex and dynamic issues
- He represents clients in complex civil actions involving substantial financial amounts and offers advice to foreign state leaders in criminal proceedings
- He has robust experience managing cases associated with federal and state False Claims Act statutes (also known as qui tam matters), and the Foreign Corrupt Practices Act
- He effectively guides clients through intricate health care fraud issues, as well as other regulatory hurdles
- Tom is a nationally recognized trial attorney
- He is a U.S. fellow with the International Academy of Trial Lawyers, an honor limited to 500 trial attorneys in the United States
- a member of the National Trial Lawyers: Top 100
- and has been noted by Chambers USA
- Tom has tried over 100 criminal and civil cases in federal and state courts throughout the nation
- He has represented national and multinational companies in civil actions with billions of dollars in dispute, and has represented individual corporate leaders and foreign heads of state in civil, criminal, and regulatory proceedings
- He has deep experience navigating dual civil-criminal proceedings and handling complex, first-of-its-kind matters in multiple jurisdictions, including matters conducted in foreign nations
- Tom previously served as United States Attorney for the Central District of California, a position to which he was appointed by President George W. Bush and unanimously confirmed by the United States Senate
- During his term, he oversaw all federal criminal and tax investigations and prosecutions, in addition to all civil matters involving the United States, within the largest federal district in the nation
- Under his leadership, his office filed record-breaking felony cases and increased complex case filings by 50 percent, including significant progress in prosecuting organized crime
- The office filed the largest gang RICO case in the history of the Department of Justice, the largest RICO case against a motorcycle gang and, for the first time in the nation, seized the gang’s trademark
- His office also filed the largest tax restitution case in IRS history
- Before his confirmation as United States Attorney, Tom served as Chief of the Criminal Division for over two years
- In this role, he was responsible for several high-profile espionage cases, helped bring the first treason case in the country since World War II, supervised multiple public corruption and civil rights cases, and oversaw some of the largest fraud cases prosecuted in the United States
- Before being selected as Criminal Chief, Tom led the office’s Civil Rights Section, where he investigated and prosecuted numerous cases, including federal hate crimes, human trafficking offenses, and police and prison guard misconduct cases
- Tom’s prosecutorial career began in San Diego County before moving to Los Angeles County as a Deputy District Attorney assigned to the Hardcore Gang Division, where he tried 35 gang murder cases
- After graduating from the United States Naval Academy, he served in the United States Navy as a Radar Intercept Officer in the F-14A Tomcat fighter, completing over 2,000 flight hours and two overseas deployments on active duty
- He is a graduate of the United States Navy Fighter Weapons School commonly known as TOPGUN
- Recognition & Leadership Awards & Accolades •Listed, The Best Lawyers in America, 2016-2026 •Criminal Defense: White-Collar, 2016-2026 •Litigation - Securities, 2023-2026 •Listed, Chambers USA Guide, Litigation: White-Collar Crime & Government Investigations •Listed, Lawdragon, “500 Leading Litigators in America,” 2025-2026 •fellow, Litigation Counsel of America •U.S. fellow, International Academy of Trial Lawyers, 2015-2024 •Selected, National Trial Lawyers: Top 100, 2011-2024 •Listed, Super Lawyers magazine, Southern California Super Lawyers, 2025 •Listed, Daily Journal, “Top White Collar Lawyers,” 2022, 2023, 2024 •Listed, Los Angeles Business Journal, “Leaders of Influence: Litigators & Trial Attorneys,” 2022 •Listed, Los Angeles Times, “Business of Law: Trends, Updates, Visionaries: Legal Visionaries,” 2022 •Recipient, Immigration and Customs Enforcement Assistant Secretary’s Award for Excellence in Law Enforcement, 2008 •Recipient, Anti-Defamation League Pacific Southwest Region, “Helene and Joseph Sherwood Prize for Combating Hate,” 2007 •Recipient, Attorney General’s “Award for Exceptional Service,” 2007 •Recipient, Los Angeles County Association of Deputy District Attorneys, “Prosecutor of the Month Award,” 2000
Practice Areas Explained
Thomas P. O'Brien's Areas of Practice
Each practice area below reflects the types of cases Thomas P. O'Brien handles, with a brief overview of what that area of law covers.
Thomas P. O'Brien is one of 20,025 white collar attorneys indexed nationally. Browse white collar attorneys in California →
Civil litigation attorneys for breach of contract, business disputes, civil rights, and class action lawsuits.
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Jurisdictional Context
Why local counsel matters in California
Practicing law in California. Legal matters in California are governed by state-specific rules of civil and criminal procedure, statutes of limitations, and substantive law. Cases originating in Los Angeles are typically filed in the local municipal court or the appropriate California state district court, depending on subject matter and amount in controversy. An attorney licensed in California brings working knowledge of local procedural deadlines, judicial practices in this andnue, and the substantive law that applies to cases brought here. Out-of-state attorneys generally cannot represent clients in California courts without local counsel or pro hac vice admission.
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