John A. Tancabel



  • Southern Methodist University Dedman School of Law (J.D., summa cum laude, 2007) Salutatorian; Order of the Coif
  • University of Dallas (B.A. in Arts in Politics, summa cum laude, 2002) Phi Beta Kappa

Areas of Practice:

Admitted to Practice:

  • Texas, 2007
  • U.S. District Courts for the Northern District of Texas
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John A. Tancabel


(214) 389-5331

Fax (214) 389-5399

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John Tancabel represents businesses and individuals in a variety of complex, high-stakes disputes in state and federal court. John has extensive experience with fiduciary duty and securities related litigation as well as disputes over control of business entities, class actions, and multi-jurisdictional litigation. John has also represented clients in white collar criminal defense matters, including internal investigations.

Before joining Diamond McCarthy, John was a judicial law clerk for the Honorable Sidney A. Fitzwater, Chief Judge of the United States District Court for the Northern District of Texas and then spent five years with the law firm of Haynes and Boone, LLP in the firm’s specialized litigation section.  
John graduated second in his 2007 law school class at Southern Methodist University, where he served as Associate Managing editor of the SMU Law Review.  


  • How Low Can You Go? An Insiders' Perspective on Selectica v. Versata and NOL Poison Pills, 39 SEC. REG. L. J. 79 (Summer 2011) (co-author)
  • Federal Discovery Practice, published in connection with a speech at the Federal Court Practice Seminar, Houston (May 2010)
  • Director and Officer Fiduciary Duties in the Context of Insolvency, published in connection with a speech at the State Bar of Texas Advanced In-House Counsel Course, Houston (July 2009) (co-author)
  • Reflections on the McNulty Memorandum, 35 SEC. REG. L. J. 219 ( Fall 2007)
  • The Honorable Sidney A. Fitzwater, Chief Judge, U. S. District Court for the Northern District of Texas (2007-2008).
  • The Honorable Jorge A. Solis, U. S. District Court, Northern District of Texas (2006) (externship)
  • United States Attorney's Office, Northern District of Texas (2005) (summer clerk)