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Mark Rush Williamson

Attorney Profile

Top Rated Family Law Attorney in Dallas, TX

O'Neil Wysocki Family Law
5323 Spring Valley Road, Suite 150
Dallas, TX 75254
Phone: 972-852-8000
Fax: 214-306-7830
Selected to Super Lawyers: 2004 - 2005, 2012 - 2015, 2019 - 2021
Licensed in Texas Since: 1985
Practice Areas: Family Law
Attorney Profile

Mark Rush Williamson is a family law attorney and partner at O’Neill Wysocki Family Law in Dallas, Texas. Mr. Williamson represents clients throughout Dallas in matters involving alimony, asset and debt division, child custody, child support, divorce, grandparents’ rights, modifications, paternity, premarital and postmarital agreements, relocation and temporary orders. He has experience representing individuals and business owners and litigating many different types of divorce, including contested, LGBT and high net worth divorces.

In his more than 35 years as a practicing attorney, Mr. Williamson has guided many Texas residents through complex family law issues. He keeps his client base small to provide personal attention to each client and work toward the best possible resolution to their unique cases. 

Regarded for his high legal capability and ethical standards, Mr. Williamson is AV Preeminent peer-review rated,* the highest rating, through Martindale-Hubbell. 

Active in his legal community, Mr. Williamson is a member of the Collin County Bar Association and the family law sections of the Dallas Bar Association and the State Bar of Texas. He is a barrister in the American Inns of Court and belongs to the Phi Delta Theta fraternity. Additionally, Texas Monthly magazine included him on its Top Lawyers of Texas list several years in a row.

In 1982, Mr. Williamson graduated from Baylor University with a bachelor’s degree in accounting. He earned his law degree from the University of Texas at Austin School of Law in 1985. He is qualified to practice law before all Texas state courts, the U.S. District Court for the Northern District of Texas and the U.S. Tax Court.

*AV®, AV Preeminent®, Martindale-Hubbell Distinguished and Martindale-Hubbell Notable are certification marks used under license in accordance with the Martindale-Hubbell certification procedures, standards and policies. Martindale-Hubbell® is the facilitator of a peer review rating process. Ratings reflect the anonymous opinions of members of the bar and the judiciary. Martindale-Hubbell® Peer Review Ratings™ fall into two categories – legal ability and general ethical standards.

Practice Areas
  • 100%Family Law
Focus Areas

Adoption, Alimony & Spousal Support, Child Support, Custody & Visitation, Divorce, Paternity, Prenuptial Agreements, Marital Property


9 Years Super Lawyers
  • Super Lawyers: 2004 - 2005, 2012 - 2015, 2019 - 2021

About Mark Rush Williamson

First Admitted: 1985, Texas

Professional Webpage:


  • Super Lawyer, Texas Monthly Magazine 2004, 2005, 2012, 2013, 2014, 2019, 2020
  • , Top-Rated Lawyer, AVVO, 2012 – 2020
  • , Top Lawyers of Texas, Texas Monthly Magazine, 2014 – 2020
  • , Top Rated Lawyers, Texas Lawyer Magazine, 2013 – 2020
  • , AV Preeminent rating, LexisNexis Martindale-Hubbell 2005 – 2020
  • Phi Delta Theta

Educational Background

  • Baylor University, BBA, Major: Accounting, 1982

Bar/Professional Activity

  • Dallas Bar Association, Family Law Section, Member: Texas Bar Association, Family Law Section, Member: Collin County Bar Association, Member: American Inns of Court, Barrister, 2021
  • U.S. Tax Court, 1987
  • U.S. District Court Northern District of Texas, 1990
  • Texas, 1985
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Office Location for Mark Rush Williamson

5323 Spring Valley Road
Suite 150
Dallas, TX 75254

Phone: 972-852-8000

Fax: 214-306-7830

Last Updated: 7/8/2021

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