Professional Summary

Sean M. Sullivan represents businesses and people in a variety of matters, including as to intellectual property rights (trademarks, copyrights, patents, and trade secrets), contracts, partnership and business management disputes, unfair competition, and class actions. Sean also has extensive experience in maritime matters, litigating cases involving injuries suffered aboard seagoing vessels, and in cases involving environmental issues. He is experienced in all phases of litigation, from pre-lawsuit investigations through trial and appeal.

Sean’s clients have spanned many industries, including aerospace, software and app development, social media, music, medical devices, aviation, architecture, craft breweries, manufacturing, visual and performing arts, banking and lending, apparel, and hi-tech and biotechnology. Prior to attending law school, Sean worked in San Diego’s biotech industry for a start-up that made products for use in immunology and molecular biology research.

Sean is admitted to practice in all state courts in California and Washington, as well as the United States District Courts for the Southern, Central, Eastern, and Northern Districts of California, the Western District of Washington, the Eastern District of Texas, and the Ninth Circuit Court of Appeals.

Representative Matters

  • First-chaired complex jury trial in San Diego Superior Court representing a software company against one of its own directors on claims for breaches of fiduciary duty. Obtained jury verdict in client’s favor.
  • First-chaired court trial in San Diego Superior Court representing company in a derivative shareholder case involving claims of breaches of fiduciary duties against management defendants brought by a pair of dissident shareholders. Decision rendered in favor of management defendants.
  • Represents national aerospace manufacturer in defense of toxic tort class action claiming nuisance and trespass from vapor intrusion of volatile organic compounds, and seeking medical monitoring remedies.
  • Represents national aerospace manufacturer in defense of toxic tort action by property owners alleging property damage resulting from ground water contamination beneath their property.
  • Successfully defended financial institution against class action claims related to ATM overdraft fees. Obtained denial of class certification, summary adjudication on nearly all claims, and eventual voluntary dismissal of entire case by plaintiff without payment of any money by the client.
  • Second-chaired federal jury trial representing a software company against claims of copyright infringement. Unanimous jury verdict obtained in client’s favor finding no infringement, and also a declaration that client owned the copyright to the software at issue. Result affirmed on appeal by the Ninth Circuit.
  • Defended software developer/marketer sued for alleged patent infringement, ending in nuisance value settlement.
  • Defended former principals of architect firm in copyright infringement, trade secrets theft, and unfair competition claims brought by their former partners. Asserted counterclaims for breaches of fiduciary duty, amongst others. Favorable settlement reached pre-trial.
  • Second-chaired federal jury trial representing a medical device distributor against claims of patent infringement. Favorable settlement reached post-trial.


  • The Best Lawyers in America®, 2022 (Commercial Litigation)
  • San Diego Super Lawyers® Rising Star - 2015-2017 (Intellectual Property Litigation)


  • Barrister, American Inns of Court – Hon. William B. Enright Inn of Court
  • Member, Association of Business Trial Lawyers
  • Irish American Bar Association of San Diego
  • Volunteer Attorney, Civil Appellate Self-Help Workshop
  • Volunteer Attorney, Pro Bono Plan of the United States District Court for the Southern District of California for the Representation of Pro Se Litigants in Civil Cases
  • San Diego County Bar Association
  • Federal Bar Association
  • American Bar Association


  • JD, University of San Diego School of Law, cum laude, Phi Delta Phi, 2007
  • BA (Biology), University of San Diego, 2001

News Coverage


  • Co-presenter. “Litigation: Big Changes or Minor Tweaks – Considerations for Managing (and Adapting) Litigation in the New Normal,” June 18, 2020.
  • Co-presenter. “Contract Drafting Tips From the Litigator’s Perspective: Avoiding Lawsuits in the Post COVID-19 World,” May 27, 2020.