O’Melveny Worldwide

Companies and educational institutions trust Dawn Sestito as their go-to outside counsel, relying on her to guide them through all manner of sensitive disputes, from arbitrations and regulatory inquiries to class-action claims and bet-the-company litigation. Drawing on her own wide-ranging commercial litigation experience and leveraging the expertise of O’Melveny specialists, Dawn builds the right teams and brings the right resources to achieve the best outcomes for clients across a range of industries.

Dawn represents some of the world’s largest companies, defending them against claims including product mislabeling, breach of contract, employment discrimination, and public nuisance—an emerging legal battleground where she has extensive experience. She has particular expertise in environmental matters, including litigation, regulatory, and administrative proceedings. As a member of the Firm’s Colleges & Universities practice, Dawn has extensive experience counseling and defending educational institutions, including in matters involving Title IX, Clery, and allegations of discrimination, harassment, and retaliation. In 2023, Dawn was recognized in Los Angeles Business Journal’s “Women of Influence: Attorneys” list for providing trusted counsel to companies and individuals across practice lines and geographies.

A respected leader within the firm, Dawn serves as Managing Partner of O’Melveny’s Los Angeles office. She previously served in several other leadership roles, including as the firm’s Southern California Litigation Regional Head, as head of the Associate and Counsel Review Committee, and as a member of the Partner Compensation Committee.

Dawn also maintains an active pro bono practice focused on marriage equality and reproductive rights. Her work helped overturn Nevada’s same-sex marriage ban, and she filed amicus briefs in several cases challenging the federal Defense of Marriage Act, including in the United States Supreme Court in United States v. Windsor

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  • Defeated class certification for major international oil and gas company in ongoing litigation stemming from accidental release at refinery
  • Won summary judgment in putative antitrust class action for major international oil and gas company
  • Representing companies across a range of industries on consumer-protection, environmental, employment, and antitrust investigations by state agencies, including the attorneys general of California and other states
  • Represented major international oil and gas company in a contract dispute with a private party; secured favorable verdict after bench-trial, including attorneys’ fees and spoliation sanctions; decision upheld on appeal by state supreme court and Ninth Circuit
  • Represented major international oil and gas company in a dispute with state over oil and gas development; defended client in two administrative hearings, two successful state court appeals, an appeal to state supreme court, and multiple separate related lawsuits; cases ultimately settled
  • Represented major international oil and gas company in litigation with federal and state governments over natural resource damages resulting from an oil spill; governments ultimately abandoned request to reopen amount of damages
  • Representing several colleges and universities facing Title IX and Clery Act sexual assault issues, including investigations and audits by US Department of Education as well as litigation brought by students, former students, and employees
  • Secured dismissal of more than a dozen putative class actions and other claims asserted against a national retail grocery chain, including claims involving consumer protection, Proposition 65, unfair competition, breach of contract, and interference with contractual and prospective economic relations; other cases ongoing
  • Represented consumer electronics companies in Section 337 investigations pending before the U.S. International Trade Commission and patent disputes pending in E.D. Texas and other district courts, including one jury trial
  • Represented financial-services firm during multi-week arbitration over business disputes with former employees, including claims of unfair competition and breach of contract
  • Secured dismissal of class-action lawsuit alleging unfair business practices and misclassification of employees by national package-delivery company
  • Secured dismissal of two class actions alleging unfair business practices, violations of the California Labor Code, and employee misclassification by biotechnology company
  • Defended large municipality in 70 individual actions alleging employee discrimination, retaliation, and violations of Section 1983 (free speech and due process)


Bar Admissions

  • California

Court Admissions

  • US District Court for the Central, Eastern, Southern, and Northern Districts of California
  • US Court of Appeals, Ninth and Second Circuits
  • United States Supreme Court


  • University of California at Berkeley, J.D.: Order of the Coif
  • University of California at Berkeley, B.A.: Phi Beta Kappa; with high distinction

Honors & Awards

  • Recognized in Los Angeles Business Journal’s “Women of Influence: Attorneys” list (2023)
  • Recommended by The Legal 500 US for General Commercial Disputes (2018-2019) and State Attorneys General (2023-2024)
  • Southern California “Rising Star” in annual surveys conducted by Law & Politics Media Inc.
  • Published in Los Angeles magazine
  • Recognized by the Daily Journal as one of California's “Top 20 under 40” attorneys for Patent Disputes and Environmental Litigation (2015)
  • Published in the Southern California edition of Super Lawyers
  • O’Melveny Values Award recipient (2005)
  • Nominated as a “Rising Star” in Litigation by Euromoney Legal Media Group at the 2014 Americas Women in Business Law Awards

Professional Activities


  • Values Award Committee