Mark is a probate litigator who focuses his practice on high-stakes trust and estate (“T&E”) disputes, as well as fiduciary litigation.

Mark E. Swirbalus

+1 617 574 4119
Mark is a probate litigator who focuses his practice on high-stakes trust and estate (“T&E”) disputes, as well as fiduciary litigation.



Mark is a probate litigator who focuses his practice on high-stakes trust and estate (“T&E”) disputes and fiduciary litigation. Mark represents individuals, families, charitable organizations, and bank and trust companies as beneficiaries, trustees, executors, administrators, and personal representatives.

He handles a broad range of T&E-related disputes, including:

  • trust and will contests involving allegations of undue influence, incompetency, and fraud;
  • breach of fiduciary duty and removal actions;
  • contested accountings;
  • trust reformation, modification, and interpretation actions;
  • irrevocable life insurance trust (ILIT) matters;
  • trust and estate property disputes;
  • family limited partnership (FLP) disputes;
  • trust-held limited liability company (LLC) disputes; and
  • reasonable deviation and cy pres matters.

Clients look to Mark not only to guide them to successful resolution of their ‘once in a lifetime’ legal matters through settlement or trial, but also to help them avoid litigation in the first place.

A Chambers High Net Worth (HNW) resource comments that Mark is “considered as Boston’s pre-eminent probate litigator.” Mark is seen as “one of the leading people in the city at what he does,” peers say. “He’s an excellent technician,” offers another resource, and “he’s got a big world view, he’s not swayed by small details. He’s a grown-up in this world – he doesn’t have to be nasty to represent his client zealously.” Other Chambers HNW resources add that Mark “has a good mind for strategy, he’s creative and a good writer,” and that Mark is “the first person I call when I have probate going to litigation.” A Chambers USA resource comments that Mark is “top notch,” "smart, and has an excellent knowledge of trust matters. He had a plan from day one to address our concerns." A fellow lawyer reports "tremendous respect for his practice. He is very strategic, smart and … very sensitive and understanding of family dynamics." This source continues: "He is able to step out and earn clients' trust and respect and take the emotion out of probate litigation."

Mark is co-Chair of the firm's Litigation group, and a Fellow of the American College of Trust and Estate Counsel (ACTEC), where he has been appointed to and serves on its Fiduciary Litigation Committee.


  • Best Lawyers in America® (2023): Litigation - Trust & Estates
  • Boston Magazine Top Lawyers, Trust & Estates, 2022
  • Chambers High Net Worth (HNW): 2016-2022 (Band 1)
  • Chambers USA, leading litigator, 2010-2013
  • Martindale Hubbell Peer Review Rated AV Preeminent™
  • Massachusetts Super Lawyers, 2009-2022
    • Top 100 Massachusetts Super Lawyers, 2016


  • American College of Trust and Estate Counsel (ACTEC), Fellow, Fiduciary Litigation Committee
  • Greater Boston Fiduciary Law American Inn of Court, Co-Founder and Former President
  • Boston Bar Association
    • Trusts & Estates Section, Public Policy Committee, 2012-2013
    • Trusts & Estates Section, Fiduciary Litigation Co-Chairman, 2010-2012
  • Boston Probate and Estate Planning Forum, Treasurer (2013-present), Moderator (2012-2013) and Program Chair (2011-2012)
  • Massachusetts Bar Association, Probate Litigation Practice Group, Probate Law Section Council, 2009-2010
  • New Hampshire Bar Association
  • Dartmouth Lawyers Association
  • Dartmouth College, Alumni Enrollment Volunteer


  • Massachusetts
  • New Hampshire


  • Dartmouth College  (B.A., 1991)
  • Boston College Law School  (J.D., 1995)