Mark G. Arnzen, Jr.

Partner

Mark is an experienced trial attorney who represents a diverse range of clients in complex litigation.  He is licensed to practice law in Ohio and Kentucky, but has also been admitted by Courts to handle specific cases in other jurisdictions, including California, Delaware, Georgia, Massachusetts, and Texas.  Mark has tried numerous cases to verdict in state and federal courtrooms, delivering opening statements, closing arguments, and cross-examining lay and expert witnesses.  At the appellate level, Mark has argued before the U.S. Court of Appeals for the Sixth Circuit and the Ohio First and Second District Court of Appeals.

Mark’s litigation experience includes prosecuting and defending claims for clients embroiled in complex business and partnership disputes (involving fraud, trade secret infringement, and contract breaches).  He also represents plaintiffs and defendants in serious personal injury matters, such as those involving traumatic brain injuries.  In one case, he recovered a multi-million-dollar settlement on behalf of his client who was assaulted and critically injured by a convicted felon acting at the direction of the client’s former employer. 

Mark’s practice also extends into the educational, construction, and logistics arenas. His clients include one of the largest private systems of schools in Ohio, as well as one of the top construction contractors in the United States.

Mark has been repeatedly recognized as one of “The Best Lawyers in America” and as a “Leading Lawyer” by Cincy Magazine.  He is Peer Review Rated AV Preeminent by Martindale-Hubbell, the highest peer rating standard given by that organization. The AV Preeminent rating is given to attorneys ranked at the highest level of professional excellence for their legal expertise, communication skills, and ethical standards by their peers.

Credentials

Education

University of Cincinnati College of Law (J.D., cum laude, 2006)

University of Dayton (B.S., 2002)

  • Business Administration

Bar admissions

  • Ohio
  • Kentucky

Court admissions

  • U.S. Court of Appeals for the Sixth Circuit
  • U.S. District Court for the Southern District of Ohio
  • U.S. District Court for the Eastern District of Kentucky
  • U.S. District Court for the Western District of Kentucky
  • U.S. Bankruptcy Court for the Western District of Kentucky

Affiliations and memberships

  • Cincinnati Bar Association
  • Kentucky Bar Association
  • City of Blue Ash, Ohio, deputy solicitor
  • City of Blue Ash, Ohio, prosecuting attorney (2007 – 2012)
  • City of Silverton, Ohio, prosecuting attorney (2007 – 2011)
  • Covington Business Council Foundation, Inc., board member (2012 – 2015)
  • Cincinnati Academy of Leadership for Lawyers (CALL) graduate, Class XX
  • National Diocesan Attorneys Association, member
  • Ohio Supreme Court Lawyer to Lawyer Mentoring Program, mentor
  • Construction Lawyers Society of America, Fellow

Distinctions

  • Best Lawyers in America®Commercial Litigation
  • Cincy Magazine Leading Lawyers
  • Peer Review Rated AV Preeminent by Martindale-Hubbell
  • Ohio Rising Stars®

Career Highlights
  • Successfully Defended Ohio Hospital at Trial

    We represented a local hospital and its employee in a lawsuit filed by a patient in the Hamilton County, Ohio Court of Common Pleas. The patient claimed that his hearing was permanently damaged because of an MRI at our client’s facility.  We tried the case for approximately one week.  After 45 minutes, the Hamilton County jury returned a unanimous verdict in favor of our client, finding that the hospital employee did not violate the standard of care for an MRI technician.

  • Successfully Defended Private High School in Lawsuit

    We successfully defended our client, a private high school, in a lawsuit challenging the principal’s decision to withdraw a student for a disciplinary infraction. The student and his family sued the school, claiming breach of contract and discrimination, and sought an injunction overturning the principal’s decision and reinstating the student. We worked in a two week span to brief the injunction request, accomplish all necessary discovery and depositions, and prepare the case for trial. After the plaintiffs presented their case, we moved for involuntary dismissal under Rule 41, arguing they had failed to meet the burden of proof required. The court agreed, and in a written decision denied plaintiffs’ motion for injunction, dismissed the injunction claim altogether, and entered complete judgment in our client’s favor on that count.  Plaintiffs then agreed to resolve the remaining damages claims for nonmonetary consideration.

News
  • August 21, 2025

    260 Dinsmore Attorneys Listed as 2026 Best Lawyers®, Ones to Watch

  • August 15, 2024

    250+ Dinsmore Attorneys Named 2025 Best Lawyers ®, Ones to Watch

  • August 17, 2023

    200+ Dinsmore Attorneys Named 2024 Best Lawyers®, “Ones to Watch”

  • March 24, 2023

    31 Dinsmore Attorneys Featured on 2023 Cincy Leading Lawyers List

  • August 18, 2022

    2023 Best Lawyers® List Recognizes 190 Dinsmore & Shohl Attorneys

  • February 8, 2022

    27 Dinsmore Attorneys From a Broad Range of Practice Areas Chosen for 2022 Cincy Leading Lawyers List

  • August 19, 2021

    Best Lawyers® Recognizes 191 Dinsmore & Shohl Attorneys

  • August 20, 2020

    Best Lawyers® Recognizes 180 Dinsmore & Shohl Attorneys