Mark Rush Williamson

Attorney Mark Rush Williamson

About Mark

Mark Rush Williamson is a family law attorney and Partner at Sullivan, Klocke & Williamson in Dallas, Texas. Mr. Williamson represents clients throughout Texas 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, Mark 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, Mark is AV Preeminent peer-review rated,* the highest rating, through Martindale-Hubbell.

Active in his legal community, Mark 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.

Professional Associations

  • Dallas Bar Association, Family Law Section, Member
  • Texas Bar Association, Family Law Section, Member
  • Collin County Bar Association, Member
  • American Inns of Court, Barrister


The University of Texas School of Law, Austin, Texas

  • J.D. – 1985

Baylor University, Waco, Texas

  • B.B.A. – 1982
  • Major: Accounting

Bar Admissions

  • Texas, 1985
  • U.S. District Court Northern District of Texas, 1990
  • U.S. Tax Court, 1987


  • Phi Delta Theta


  • Super Lawyer, Texas Monthly Magazine 2004, 2005, 2012, 2013, 2014, 2019, 2020, 2021
  • AV Preeminent rating, LexisNexis Martindale-Hubbell 2005 – 2022
  • Top Rated Lawyers, Texas Lawyer Magazine 2013 – 2021
  • Top Lawyers of Texas, Texas Monthly Magazine 2014 – 2021
  • Top-Rated Lawyer, AVVO 2012 – 2022

Avvo Top Attorney badge for Mark Rush Williamson

Avvo Rating: 10.0 – Top Attorney

SuperLawyers badge for Mark Rush Williamson

Rated by Super Lawyers