Co-leader of Chicago Office Litigation & Dispute Resolution

J. Gregory Deis

Global Investigations & White Collar Defense, Litigation & Dispute Resolution, Global Anti-Corruption & FCPA

“He provides practical and strategic advice that reflects commercial realities. [He] is extraordinarily talented.” (2022)

“[A] top-flight white-collar lawyer” and “an outstanding trial lawyer.” (2020)

Chambers USA


Greg Deis is a former Assistant U.S. Attorney who currently serves as global co-chair of Mayer Brown's Global Investigations & White Collar Defense practice and co-leader of Mayer Brown’s Litigation & Dispute Resolution Practice in Chicago. Greg regularly represents clients in high-stakes criminal and regulatory investigations and complex civil litigation. A Fellow of the American College of Trial Lawyers, Greg is a seasoned trial lawyer, having served as lead trial counsel in numerous civil and criminal trials and arbitrations.

Greg has been recognized as a leading lawyer by Chambers USA since 2019. In Chambers USA 2021 clients note that he is "super personable, good in court and…an excellent investigator – a truly terrific lawyer” with an “incredible balance of intelligence and patience – he exudes calmness." Greg is also recognized in Legal 500 USA with one client commenting: “Greg Deis is a standout. A skilled advocate and counselor.” Lawdragon 500 has also recognized Greg as a leading litigator in the U.S.


Representative experience includes:

White Collar Defense

  • Electric vehicle manufacturer in DOJ and SEC investigations relating to allegations concerning revenue recognition, public disclosures and insider trading; SEC investigation closed with no action.
  • Represent Fortune 50 company, former senior officer of Fortune 100 subsidiary and several members of Illinois General Assembly in DOJ investigation of alleged public corruption focused on former Illinois House Speaker Michael Madigan.
  • Large food manufacturer in DOJ Antitrust criminal investigation focused on alleged price fixing in connection with USDA bid.
  • Technology company in DOJ Antitrust investigation; DOJ closed investigation with no action against client.
  • Fortune 500 medical device company in a parallel DOJ civil/criminal False Claims Act investigation; DOJ declined to intervene.


  • University of Illinois College of Law, JD, summa cum laude
    Order of the Coif, valedictorian
  • Marquette University, BS, Civil & Environmental Engineering


  • Illinois