Katie L. Viggiani

Katie L. Viggiani
Partner

250 West 55th Street

New York, NY 10019-9601

kviggiani@mofo.com

(212) 336-4212

BAR ADMISSIONS

New York

EDUCATION

The George Washington University, B.A.

University of California, Los Angeles, School of Law, J.D.

Katie is a versatile commercial litigator who represents U.S. and international companies in complex commercial disputes, consumer class actions, and privacy and data-related litigation in courts and arbitral tribunals throughout the country. She develops strategies that look beyond the dispute at hand to advance clients’ holistic goals inside and outside the courtroom. Her clients include technology, retail, e-commerce, healthcare, and financial services companies, from start-ups to Fortune 500 companies. She is a former co-chair of Morrison Foerster’s Complex Litigation + Advisement Group.

Consumer Class Actions and Privacy Litigation

Katie regularly represents companies in consumer class actions, including cases asserting privacy claims based on novel and evolving theories of liability. She has defended companies against claims under federal wiretap statutes, the Illinois Biometric Information Privacy Act, the California Invasion of Privacy Act, and other privacy laws. She also defends companies in high-profile litigation involving data security and the handling of sensitive information.

Mass Arbitration, Mass Torts, and Multijurisdictional Claims

Katie helps companies navigate mass arbitrations—the coordinated filing of large numbers of nearly identical claims—including matters involving parallel class actions. She has guided clients to favorable resolutions and outcomes in these matters. Her practice also includes defending companies in serial mass tort and class action litigation across multiple jurisdictions. In 2023, The Legal 500 recommended Katie in Product Liability, Mass Tort and Class Action Defense.

Arbitration, Trial, and Enforcement Experience

Katie has extensive arbitration experience in high-stakes commercial disputes. Most recently, she co-led the defense of a commercial dispute in a full merits hearing before a three-arbitrator AAA panel, examining fact and expert witnesses and presenting the client’s case on the merits. She was also part of a trial team that represented the founder and former CEO of a high-tech company in a criminal prosecution alleging stock option backdating and improper revenue recognition. The team achieved two separate trial victories, obtaining acquittal on six counts and a hung jury on the remaining count.

Katie also represents clients in government investigations and enforcement actions, including matters involving securities fraud, benchmark manipulation, market manipulation, tax evasion, and accounting issues brought by the U.S. Department of Justice, Securities and Exchange Commission, Commodity Futures Trading Commission, and Financial Industry Regulatory Authority.

More About Katie

Katie maintains an active pro bono practice focused on indigent criminal defense, civil rights, and legal issues facing the LGBTQ+ community. She was a founding member of the firm’s NY LGBTQ+ Affinity Group and is an active member of the MoFo Proud Network and the firm’s Women’s Strategy Committee.

Katie earned her J.D. from the UCLA School of Law, where she was a managing editor of the UCLA Women’s Law Journal. While in law school, she worked as a law clerk for the Los Angeles County Public Defender and was a member of UCLA’s Criminal Defense Clinic.

Rankings

Listed as Notable Practitioner in Litigation: General Commercial (New York)

Chambers 2026

Listed as Notable Practitioner in Privacy & Data Security: Litigation

Chambers 2026

Recommended for Media, Technology and Telecoms: Advertising and Marketing

The Legal 500 US 2025

Recommended for Dispute Resolution: General Commercial Disputes

The Legal 500 US 2025

Recommended for Dispute Resolution: Product Liability, Mass Tort and Class Action – Defense: Consumer Products (Including Tobacco) 

The Legal 500 US 2023