Image: Mark Deethardt
Mark R. Deethardt
Hancock Whitney Center
701 Poydras Street
Suite 5000
New Orleans, Louisiana 70139


Mark is a litigator in the firm’s New Orleans office whose practice focuses on energy, environmental, and toxic tort litigation, as well as other litigation matters. 

Before joining the firm, Mark was an associate with a large New Orleans-based defense firm where he maintained a diverse litigation practice.  There, Mark routinely represented highly regulated national and regional financial institutions and banks in consumer financial services litigation involving single plaintiffs and class actions.  Mark represented a variety of other businesses – both large and small – in complex commercial litigation, property and insurance disputes, tax title recovery, and other tort and personal injury cases.  Mark is also experienced at protecting and preserving clients’ rights on appeal.  He has authored numerous successful merits briefs and defended writ applications before all Louisiana courts of appeals, the Louisiana Supreme Court, and the United States Court of Appeals for the Fifth Circuit.      

Mark graduated magna cum laude from LSU Law in 2012 where he was elected to the Order of the Coif and served as a Junior Associate and Senior Editor on the Louisiana Law Review.  As a Junior Associate on the Law Review, Mark received the Vinson & Elkins Award for Outstanding Student Case Note or Comment.  Before entering private practice, Mark served as a judicial law clerk to the Honorable Jeanette Theriot Knoll, former Associate Justice of the Louisiana Supreme Court. 



  • IEL’s Young Energy Professionals publication, The Energy Dispatch

  • The Foundation For Natural Resources and Energy Law, Member

  • Louisiana Oil & Gas Association, Member

    • Legal Committee, Member

  • Federal Bar Association

  • Louisiana Bar Association

  • New Orleans Bar Association


  • Homeless Experience Legal Protection Program – Volunteer Attorney


  • Best Lawyers "One to Watch", 2022
  • Louisiana Super Lawyers “Rising Star,” 2016-2018, 2020-2022
  • Louisiana State Bar Association, Leadership LSBA Class, 2015-2016


Mark R. Deethardt
Rated by Super Lawyers

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After Hours

"I was born and raised in New Orleans, and one of the things I love most about the city is its music culture.  Whether it’s going to see live music or collecting records, I am an avid music fan and try to incorporate music into my life on a daily basis.   My wife, Shannon, and I also love taking advantage of everything else New Orleans has to offer, including its restaurants, art galleries, and non-stop festivals.  We are both attorneys too, so when we are not in the office, we like to remain as active as possible by running, cycling, training, and everything in between."