Mark P. O’Brien, III

Estate Planning & Trust Administration Attorney

Mark O’Brien is an associate attorney who works with families to create an estate plan that best suits their needs and desires, to create tax advantageous strategies, to avoid probate and negate family disputes; as well as helps families navigate the difficult and complex probate and/or trust administration process, and any related court matters. Mr. O’Brien also advises clients who require assistance with guardianships and conservatorships. Prior to becoming an attorney, Mr. O’Brien worked as a paralegal for over a decade, including 6 years as a paralegal at Merhab Robinson & Clarkson.

Experience and Practice Areas

• Estate Planning
• Estate & Gift Tax Planning
• Real Property Tax Planning
• Charitable Planning
• Probate Administrations
• Trust Administrations
• Guardianships and Conservatorships
• Fiduciary Accountings
• Generational Wealth Transfer Planning
• Business Succession Planning

Bar Memberships/Associations

Mr. O’Brien is a member of the Orange County Bar Association, as well as the Trust & Estates Section of the OCBA. Mr. O’Brien is admitted to California State Bar and the Federal District Court, Central District of California.


Mr. O’Brien attended California State Polytechnic University, Pomona (CCP) where he earned his B.S. in Finance, Real Estate and Business Law (2011). In 2012, Mr. O’Brien obtained his ABA Paralegal Certificate from California State University, Los Angeles (CSULA). In 2017, he completed a taxation program at the University of California, Los Angeles (UCLA).

Mr. O’Brien attended University of La Verne College of Law (ULV-COL; ABA accredited portion) and graduated cum laude in May 2022.  While at ULV COL, Mr. O’Brien received seven (7) CALI awards for excellence in Constitutional Law, Trial Advocacy, Criminal Procedure & Investigation, Mediation, Negotiation, Business Organizations, and Transactional Workshop.