Kostas D. Katsiris

Katsiris Kostas

Kostas Katsiris is an accomplished commercial litigator and powerful advocate for his clients. Kostas represents plaintiffs and defendants in complex disputes in federal and state courts in New York and throughout the United States, and in private mediations and arbitrations. Clients in financial services, real estate, media and entertainment, retailing, transportation and logistics, hospitality, and hotel management seek his counsel and advocacy in all manner of disputes, including securities actions, contract disputes, business torts, data security breaches, corporate governance disputes, and bankruptcy-related matters.

Kostas is equally comfortable representing plaintiffs and defendants and is known for his zealous and creative advocacy. His diverse experience spans the entire process of litigation and arbitration, from the investigation and pleading stages through discovery and trial. In the class action arena, Kostas has been involved in some of the largest class actions on record and has defeated class certification and narrowed claims through motion practice. He has also served as a federal court-appointed special master in a complex consumer fraud class action.

Kostas regularly represents banks, investment advisors, hedge funds, private equity firms, broker-dealers, and officers and directors in civil litigation and regulatory proceedings. He also represents real estate developers, landlords, and commercial tenants in breach of contract and business tort cases; hotel management companies in disputes concerning management and franchise agreements; special servicers in the Commercial Mortgage-Backed Security (CMBS) industry; and other high-profile clients in a number of different industries.

Kostas also has substantial experience conducting confidential internal investigations relating to sensitive legal issues.


Representative Matters

Financial Services Industry

  • Represented clients in securities actions brought under federal and state securities laws
  • Defended against stockholder class actions arising out of merger agreements
  • Represented clients in Securities and Exchange Commission (SEC) and Financial Industry Regulatory Authority (FINRA) matters, including internal investigations concerning reporting obligations and conduct
  • Represented defendants in breach of contract disputes and business torts, including claims of tortious interference; won dismissal of suits alleging in excess of $50 million in damages
  • In plaintiff’s-side matters, has recovered millions of dollars for clients, and helped them restructure business and contractual arrangements

Real Estate, Hotel Management, and Construction

  • Defeated negligence and nuisance claims against the nation’s largest deconstruction and abatement company, related to the reconstruction of the World Trade Center area in Lower Manhattan; the defense theory was later adopted by other, similarly situated defendants
  • Obtained dismissal of fraud claims brought by a prominent New York City–based landlord against an international developer of surgical centers
  • Represented a global hotel management company in litigation brought by the owner of a prominent Miami Beach hotel
  • Defended a real estate developer’s ability to complete the renovation of a building in Manhattan and defeated claims of injunctive relief brought by an adjacent landowner
  • Represented the senior lender and various junior lenders in inter-creditor disputes arising out of the multi-billion-dollar financing of Peter Cooper Village and Stuyvesant Town
  • Represents a New York City-based real estate investor and developer in connection with a dispute involving another developer’s ability to build two large residential towers on adjacent land; involves the rights and obligations of a Zoning Lot Development Agreement (ZLDA)

Bankruptcy-Related Disputes

  • Represented a prominent private equity firm in litigation arising out of the bankruptcy of one of its portfolio companies, a well-known mortgage lender; involved bankruptcy-related claims asserted by an unsecured creditor’s committee, as well as securities-related tort claims asserted by sophisticated hedge fund creditors
  • Represented a leading global investment bank and underwriter of asset-backed securities in an adversary proceeding brought by a litigation trustee in federal bankruptcy court
  • Represented an investment adviser and its affiliates in Chapter 15 proceedings related to an application by debtors for recognition of restructuring proceedings in the Cayman Islands
  • Represented clients in preparing responses to expedited discovery requests, pursuant to Rule 2004
  • Represents the interests of distressed debt investors in the bankruptcy context

Class Actions

  • Obtained an order denying lead plaintiffs’ motion for class certification in a putative shareholder class action; order was based on testimony elicited during the depositions of lead plaintiffs
  • Represented a Big Four audit firm in various state court actions and in consolidated federal securities and derivative actions related to alleged misconduct by officers of the international manufacturing company Tyco
  • Represented a global retailer in privacy-related class actions filed in multiple jurisdictions that alleged the misuse of customer information
  • Served as a federal court-appointed special master in a complex consumer fraud class action involving hidden images in a well-known video game; oversaw the notice and claims administration procedures




  • J.D. cum laude University of Pennsylvania Law School 1999
  • Moot Court Board, Co-Chair

    University of Pennsylvania Law Review, Articles Editor

  • B.B.A. High Distinction University of Michigan 1996

Bar Admissions

  • New York

Court Admissions

  • U.S. Court of Appeals for the Second Circuit
  • U.S. Court of Appeals for the First Circuit
  • U.S. District Court for the Southern District of New York
  • U.S. District Court for the Eastern District of New York

Clerk Experience

  • Honorable Shirley Wohl Kram U.S. District Court for the Southern District of New York 1999 2001

Professional Memberships and Activities

  • Member, Federal Bar Council
  • Member, Hellenic Lawyers Association of New York
  • Member, International Bar Association
  • Member, New York City Bar Association; Secretary, Government Ethics Committee, 2008 - 2011


  • Super Lawyers
    • New York Metro, 2017 – 2020
    • Rising Stars, New York Metro, 2013 – 2014
  • Greek America Foundation, Greek America’s Forty Under 40, 2012
  • Legal 500, Technology: Data Protection and Privacy, 2012



  • Served as a mentor to young adults and teenagers through the Year Up and Citizen Schools programs