Chelsea Cosillos focuses her practice on general commercial litigation matters, as well as class actions and other complex litigations in federal and state courts and arbitration proceedings.


  • Representing a major health insurer in a variety of matters, including arbitration of disputed contract terms, as well as cases involving ERISA, breach of contract, and antitrust claims*
  • Represented a home textile manufacturer in defense of putative class actions alleging product mislabeling, including successful defense to challenges in multiple courts to class-wide settlement*

*Matter handled prior to joining McDermott



  • Empire State Counsel Program Honoree, 2018


Harvard Law School, JD, 2018
Arizona State University, BS, summa cum laude, 2013

New York

Chelsea Cosillos

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