Katherine Mateo

Katherine Mateo is a skilled litigator with extensive experience in resolving complex, high-stakes commercial disputes for prominent companies and individuals.

For nearly a decade, Kat has helped clients navigate claims and investigations. From single-plaintiff cases to class actions, she has achieved favorable results at trial, on appeal, through arbitration, mediation and negotiated settlement.

Kat has handled a range of commercial disputes including those involving intellectual property, securities, fraud, breach of contract, white-collar defense, transactional matters, bankruptcy, antitrust, and toxic tort. She has prevailed in cases related to residential mortgage-backed securities and Foreign Corrupt Practices Act (FCPA) investigations, has steered clients through internal investigations, and successfully defended both individual and corporate clients in major cross-border criminal investigations.

Multinational companies, financial institutions, executives and directors, and high-net-worth individuals rely on Kat’s broad experience throughout all phases of litigation, from crafting pretrial strategies and settlements to trials, appeals, and alternative dispute resolution mechanisms. Working closely with her clients, she identifies pragmatic, cost-effective strategies that manage risk and align with each client’s business objectives and needs. With her clients’ goals front and center, she focuses on the critical issues at stake, positioning clients for successful outcomes at every case stage.

Clients praise Kat for her calm manner in stressful situations and frequent communication, informing them of all case and matter issues and developments. Known for her enthusiasm in practice and a long-standing commitment to diversity and inclusion, Kat previously served as the head of an affinity group for attorneys and staff members of color and is currently a member of Olshan’s Diversity & Inclusion Committee.

Before joining Olshan, Kat was a litigation associate at Morrison & Foerster. She is fluent in Spanish.

  • Obtained summary judgment for the plaintiffs in a case valued at greater than $100M involving a dispute over under-delivery of shares in the cashless exercise of warrants. OTA LLC, et al. v. Willscot Mobile Mini Holdings Corp. (N.Y. Sup., County of Westchester).
  • Obtained summary judgment for defendants in a consolidated action concerning a dispute over partnership status and alleged violations of fiduciary duties. Rowen Seibel, et al. v. Jude Jeffrey Frederick, et al. (Nevada District Court, Clark County).
  • Favorably settled a dispute for the defendant in federal action for disgorgement of profits under Section 16(b) of the Securities Exchange Act of 1934 (S.D.N.Y.).
  • Obtained summary judgment for the plaintiff in a federal declaratory judgment action involving alleged infringement of trademarks. Now-Casting Economics, Ltd. v. Economic Alchemy LLC (S.D.N.Y.).


Honors & Recognitions

  • Listed among the “40 Under 40 Rising Latino Stars” by The Hispanic Coalition NY, Inc.
  • Recognized as “One to Watch” in The Best Lawyers in America® for Litigation - Securities Law, 2024


  • Dominican Bar Association
  • New York City Bar Association

Practice Areas


J.D., Stanford Law School, 2014

  • Article Editor, Stanford Journal of Law, Science, and Policy
  • Senior Editor, Stanford Law and Policy Review

B.A., summa cum laude, Macaulay Honors College (CUNY), 2011

  • Phi Beta Kappa


  • New York


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