Felicia H. Ellsworth

Felicia Ellsworth is an experienced trial and appellate litigator, and a member of both the Appellate & Supreme Court Litigation Group and Business Trial Group. Her trial practice focuses on high-stakes complex commercial litigation in both state and federal courts, and her appellate practice spans both civil and criminal matters in the state and federal appeals courts, including the Supreme Court of the United States.

Ms. Ellsworth has represented numerous clients in commercial disputes on a wide range of legal issues including antitrust, contract law, real property, administrative law and procedure, and constitutional law. She has also represented clients in both civil and criminal appeals involving patent infringement, contract law, constitutional law, and criminal law and procedure. Ms. Ellsworth has represented clients in state administrative tribunals, Massachusetts Superior Court, and in state appellate courts, including the Supreme Judicial Court of Massachusetts. Ms. Ellsworth’s federal practice spans numerous district courts as well as the United States Courts of Appeals for the First, Second, Fourth, Fifth, Sixth, Ninth, Tenth and Federal Circuits; and in the Supreme Court of the United States. She has argued before both federal and state appeals courts, including the First, Second and Sixth Circuits, and the Massachusetts Appeals Court.

As co-chair of the firm's Pro Bono and Community Service Committee, Ms. Ellsworth also maintains a robust pro bono practice, including representing clients in constitutional cases, criminal appeals, immigration proceedings and civil rights actions.

Pro Bono and Community Involvement

Throughout her time at the firm, Ms. Ellsworth has become deeply involved in numerous pro bono matters. She played a lead role in WilmerHale’s representation as co-counsel with the Commonwealth of Massachusetts in the Commonwealth’s challenge to the constitutionality of DOMA, leading to the historic Supreme Court ruling favoring marriage equality. Ms. Ellsworth remained involved in the fight for marriage equality after participating in the challenge to DOMA and helped lead the firm's representation of Gay and Lesbian Advocates and Defenders in various federal courts of appeals considering marriage equality issues in the Fourth, Sixth, Seventh and Tenth Circuits prior to the Supreme Court’s Obergefell decision.

In addition to her marriage equality pro bono representations, Ms. Ellsworth has a robust pro bono practice that includes representing individuals seeking asylum based on religious and gender persecution and individuals appealing their criminal convictions and sentences. She is a member of the First Circuit Court of Appeals Criminal Justice Act panel, through which she provides pro bono representation to indigent defendants on appeal.

Professional Activities

Ms. Ellsworth is admitted to practice in the Commonwealth of Massachusetts and before the United States District Court for the District of Massachusetts, Colorado, and Michigan, and the United States Courts of Appeals for the First, Second, Sixth, Ninth, Tenth, and Federal Circuits, and the Supreme Court of the United States. In 2017, she was appointed by the Justices of the Supreme Judicial Court of Massachusetts to the Standing Advisory Committee on Rules of Civil and Appellate Procedure for the Massachusetts Court System. She is an elected member of the American Law Institute, a member of the Board of Trustees of the Women’s Bar Foundation, and a member of the Boston Bar Association and the Women’s Bar Association.

Past Experience

Ms. Ellsworth served as a Special District Attorney in the Middlesex District Attorney's Office in 2010 and 2011, where she prosecuted cases involving violent crimes, financial fraud, and many other offenses. Previously, Ms. Ellsworth served as a law clerk to Chief Justice John G. Roberts, Jr. of the Supreme Court of the United States, and Chief Judge Michael Boudin of the United States Court of Appeals for the First Circuit. During law school, Ms. Ellsworth served as editor-in-chief of The University of Chicago Law Review and interned with the United States Attorney's Office for the District of Massachusetts.


  • Defending against putative class action lawsuits in federal and state court arising out of a recent highly publicized data breach.

  • Representing multinational networking equipment manufacturer in a patent infringement appeal in the Federal Circuit and Supreme Court. 

  • Leading the WilmerHale team representing the State of Vermont in various matters relating to the proposed relicensing, decommissioning, and sale of the Vermont Yankee Nuclear Power Station in administrative proceedings before the Vermont Public Utility Commission.

  • Helping to lead the WilmerHale team in filing a brief in Obergefell v. Hodges, concerning government recognition of the freedom to marry, on behalf of a total of 303 Republican, libertarian, conservative and center-right high-profile activists and government officials, including past presidential candidates, seven current and former governors, and 23 current and former members of the House of Representatives and US Senate. The brief received significant media attention when filed.

  • Representing a private beverage company in the Ninth Circuit and Supreme Court in an important Lanham Act case, resulting in a unanimous ruling in the client's favor in a case that attracted significant press coverage, including in The New York Times and Law360.

  • Helping to lead the WilmerHale team in filing amicus briefs on behalf of Gay & Lesbian Advocates & Defenders in the Fourth, Fifth, Sixth, Seventh, and Tenth Circuits in appeals arising out of challenges to same-sex marriages bans in several states.

  • Representing a multi-national oil and gas company in several matters as part of a litigation in which tens of billions of dollars in damages are sought from energy industry companies based on allegations that oil and gas development work over many decades has damaged coast property in Louisiana and made it more vulnerable to flood damage.

  • Representing a medical device manufacturer in a successful appeal to the Supreme Judicial Court of Massachusetts involving damages and injunctive relief.

  • Presenting oral argument on behalf of appellee American Honda in W&D Imports Inc. v. Lia. Five days after oral argument, the panel issued a summary order affirming the decision in American Honda's favor. 

  • Filing numerous amicus curiae briefs in both in the Supreme Court, Federal Circuit and other courts of appeals addressing a variety of different topics. Most recently, Ms. Ellsworth filed an amicus brief in support of certiorari on behalf of a group of Internet industry companies in Spokeo Inc. v. Robins.    

  • Represented the Berkshire Museum in multiple appellate proceedings and a wide-ranging investigation by the Massachusetts Attorney General in relation to the Museum’s art collection, including two paintings by Norman Rockwell.


  • Award Text

    Recognized as a Trial Rising Star



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    Named to the Top Women of Law List

    Massachusetts Lawyers Weekly


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    Selected as a Massachusetts Super Lawyer for Appellate

    Super Lawyers


Insights & News


  • Education

    • JD, University of Chicago Law School, 2005

      High Honors Order of the Coif; Editor-in-Chief, The University of Chicago Law Review
    • BS, Foreign Service, Georgetown University, School of Foreign Service, 2000

      cum laude Honors Certificate in Muslim-Christian Understanding
  • Admissions

    • Massachusetts

  • Clerkships

    • The Hon. Michael Boudin, US Court of Appeals for the First Circuit, 2005 - 2006

    • The Hon. John G. Roberts, Jr., US Supreme Court, 2006 - 2007