Ann O'Brien

Baker & Hostetler LLP

My Contact Information

Baker & Hostetler LLP
Washington, DC
Phone 1: 202.861.1650

Social Links


Washington DC


Ann O'Brien focuses her practice on advising and counseling businesses facing civil antitrust, criminal cartel, or complex white collar investigations or litigation. Ann’s insight on antitrust agency priorities, goals, and policies, are a valuable asset to companies facing international and multi-agency exposure. She has substantial experience leading every aspect of domestic and international antitrust and white collar investigations and prosecutions, including litigating federal criminal jury trials. Additionally, Ann provides clients with cutting-edge compliance counseling and training that can help deter or quickly detect antitrust exposure, informed by what is most important to the Antitrust Division and the courts.

Ann has extensive knowledge of antitrust enforcement practices and policy decisions, gained from her time working at the U.S. Department of Justice in the Antitrust Division and as a Special Assistant United States Attorney in the District of Maryland. During her nearly 20-year tenure, she assumed numerous senior leadership and management positions in the Antitrust Division, notably as the Assistant Chief of two sections and as the Acting Director of Criminal Enforcement. She was involved in virtually every major criminal enforcement and policy decision made by the Antitrust Division for nearly two decades, and reviewed and approved hundreds of case recommendations, leniency recommendations, search warrants, and requests for grand jury or preliminary inquiry authority. Notably, she gained comprehensive knowledge of antitrust corporate compliance and developed strong relationships with domestic and foreign antitrust enforcers and regulators.

Having established herself as a thought leader in the antitrust community, Ann regularly speaks and writes on a broad-range of antitrust topics. She has also trained hundreds of antitrust prosecutors and law enforcement agents, and served as a liaison to other DOJ components and government agencies. Utilizing her in-depth understanding of antitrust policy and prosecution, Ann skillfully guides clients through their unique antitrust and white collar matters.

Practice Areas

  • Anti-Corruption
  • Antitrust
  • Compliance Counseling
  • Corporate Crime
  • Extradition
  • Foreign Corrupt Practices Act
  • Government Investigations
  • White Collar Crime

Law or Graduate School Name

  • Northeastern University School of Law