William A. O’Leary

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Prior to joining León Cosgrove Jiménez, LLP, Mr. O’Leary served as a career judicial law clerk to the Honorable James Lawrence King, U.S. District Judge of the U.S. District Court for the Southern District of Florida. In that role, he drafted numerous opinions and maintained primary responsibility for the court’s civil docket, where he was exposed to a wide variety of cases arising under many different practice areas. This experience has given him a unique insight into effective legal writing and oral advocacy, as well as a strong grasp of the Federal Rules of Civil Procedure and the Federal Rules of Evidence.

Mr. O’Leary attended the University of Florida Levin College of Law, where he graduated magna cum laude while serving as the vice-president of the Justice Campbell Thornal Florida Moot Court Team, a teaching assistant for a legal writing professor, an editor of the Florida Journal of Law and Public Policy, and a summer associate for in-house counsel to a Fortune 500 company.


The State of Florida in an action alleging a nationwide scheme of deceptive advertising in connection with mortgage relief services.

An individual sued by the Republic of Trinidad and Tobago under the Racketeer Influenced and Corrupt Organizations Act (RICO), initially seeking damages of more than $100 million.

A Bahamian company relating to an investigation by a federal agency for alleged violations of the Foreign Corrupt Practices Act.

An individual in a civil rights case against correctional officers based on the use of excessive force.

Practice Areas

Commercial Litigation

Honors & Awards

Order of the Coif

Order of the Barristers

Book Awards in Florida Civil Procedure, Trial Practice

Best Oralist, Zimmerman Kiser Sutcliffe Moot Court Final Four Competition

Best Brief Winner and Finalist, E. Earle Zehmer National Moot Court Competition

Best Team, Raymer F. Maguire Appellate Advocacy Competition

Court Admissions



J.D., University of Florida Levin College of Law, magna cum laude, 2019

B.A., Catholic University, magna cum laude, 2016




Hon. James L. King, U.S. District Court for the Southern District of Florida