Experienced Healthcare, Antitrust, Commercial & Corporate Litigation Attorney
Grant Petrosyan is a Partner in the firm’s Healthcare and Litigation Practices and Co-Chair of the firm’s Antitrust Practice. An experienced litigator, Grant represents clients in complex, high-stakes disputes across a wide range of industries. Grant’s practice focuses on business, complex commercial litigation and antitrust litigation matters.
Grant has substantial experience handling matters in federal and state courts, as well as in arbitration proceedings, and regularly represents businesses, healthcare providers, and individuals at every stage of litigation—from pre-suit strategy through discovery, motion practice, trial and appeal. Grant is known for developing practical, results oriented strategies tailored to each client’s objectives. Grant is particularly adept at managing complex, multi-party disputes involving significant legal and factual issues, and navigating the procedural and strategic challenges presented in both litigation and arbitration settings.
Grant maintains a broad-based litigation practice and handles a diverse array of matters including, contract disputes, shareholder and corporate governance disputes, antitrust and competition-related litigation, business torts, including fraud and unfair competition claims, and healthcare-related litigation, including disputes involving provider networks and reimbursement.
Grant prioritizes a pragmatic and client-focused approach to litigation. Whether prosecuting claims or defending against significant exposure, Grant is committed to delivering effective advocacy and achieving results at every stage of the dispute.
He is admitted to practice in New York and New Jersey, as well as before the United States District Court for the Eastern District of New York. Grant is a member of the American Bar Association, the New Jersey State Bar Association, and serves on the Board of Governors of the Armenian Bar Association. He was recently recognized as a Rising Star by the Armenian Bar Association. *
*No aspect of this advertisement is approved by the American Bar Association. The standard of methodology for this award can be found here.
*No aspect of the advertisement or award(s) listed below has been approved by the Supreme Court of any state or the American Bar Association. A description of the standard or methodology used can be found here.
Rising Star by the Armenian Bar Association*
American Bar Association
New Jersey State Bar Association
Board of Governors of the Armenian Bar Association
“Spoliation Of Evidence Is A Risky And Shortsighted Strategy,” Law360, June 10, 2025.
“The US President Joe Biden signs a sweeping executive order to promote competition, including the formation of the White House Competition Council, and directs federal agencies to crack down on anticompetitive practices and concentrated markets,“ Concurrences, July 9, 2021.
“The US State of New York Senate proposes legislation to modernize its antitrust law and expand the state’s and private litigants’ ability to litigate against companies for anticompetitive conduct,” Concurrences, September 14, 2020.
“The US District Court for the Northern District of California finds that an athletic association’s cap on grants given to athletes is an anticompetitive restraint of trade (NCAA / Alston),” Concurrences, March 8, 2019.
“DOJ’s Probe into Four Automakers: Impartial Investigation or Politicization of Antitrust?” Competition Policy International, October 29, 2019.
“The Airbus and Boeing Duopoly: Would More Aggressive Antitrust Enforcement Benefit the
Commercial Aviation Industry?” Competition Policy International, April 2019.
American Antitrust Institute – Competition Roundtable: The Darkest Side of Rising Concentration – Fear and Retaliation in Antitrust (October 2021)
American Bar Association – Antitrust Section – The Importance of Preventing Biosimilar Disparagement (June 2021)
Armenian Bar Association – Crypto & Blockchain: What Lawyers Need to Know (May 2021)
The Peter J. Tobin College of Business at St. John’s University – Overview of Epic Games v. Apple (November 2020)
The Peter J. Tobin College of Business at St. John’s University – Overview of T-Mobile / Sprint Merger (April 2020)
Mandelbaum Barrett Launches Antitrust Practice In NJ – Law360 Pulse
With Litigation Over Competition Rising, Mandelbaum Barrett Launches Antitrust Practice | Law.com
Mandelbaum Barrett Launches Antitrust Practice – New Jersey Business Magazine
Mandelbaum Barrett PC debuts antitrust practice | ROI-NJ
CPI | Mandelbaum Barrett PC Expands Legal Offerings With Strategic An…
New Jersey
New York
United States District Court for the Eastern District of New York
United States District Court of New Jersey
Healthcare Litigation Team Secures Emergency Relief on Behalf of Hospital against Major Insurance Company
August 14, 2025
Our Healthcare Litigation Team, led by Mohamed H. Nabulsi, Steven I. Adler, and Grant Petrosyan, recently prevailed in obtaining emergency injunctive relief on behalf of a long-term acute care hospital whose facility participating provider agreement was wrongfully terminated by one of the largest insurance companies. The decisive victory ensures that the hospital can continue providing critical, uninterrupted care to its patients and residents—many of whom have complex and serious medical and therapeutic needs.Mandelbaum Barrett PC’s Healthcare Litigation Group Obtains a Pre-Answer Dismissal in a Business Dispute Against a Medical Practice and its Shareholder-Physician
June 2, 2025
Mandelbaum Barrett PC’s Healthcare Litigation Team led by Mohamed H. Nabulsi, Joseph M. Franck, and Grant Petrosyan obtained a significant pre-answer dismissal of a complaint in a New Jersey State Court Action filed against a medical practice and its shareholder-physician. The litigation was filed by a corporation seeking to hold the medical practice liable under […]Paging Cybersecurity: Healthcare Providers Need to Make a “Change” to Protect Themselves, and Their Patients, Against Cyberattacks
April 30, 2024
In February 2024, the healthcare industry was rattled by a significant cyberattack targeting Change Healthcare (“Change”), a subsidiary of UnitedHealth Group, one of the largest health insurance companies in the world. The breach sent shockwaves throughout the healthcare ecosystem, raising concerns about patient data security, operational integrity, and the vulnerability of critical infrastructure. As the […]Mandelbaum Barrett’s Antitrust Practice Earns Law360 and NJLJ Spotlight
May 27, 2026
Mandelbaum Barrett PC’s newly launched Antitrust Practice is generating significant media attention, with both Law360 Pulse and the New Jersey Law Journal highlighting the firm’s strategic expansion and the growing demand for antitrust counsel amid increased enforcement and litigation activity. Together, the coverage reinforces the timely launch of the practice, led by co-chairs Harrison McAvoy […]Mandelbaum Barrett Launches Antitrust Practice to Meet Rising Counseling and Litigation Demands
May 19, 2026
As antitrust and competition law take on growing significance—driven by increased federal and state enforcement, expanding private litigation, and heightened scrutiny of pricing and transactions—Mandelbaum Barrett PC has formally launched an Antitrust Practice to help clients address these developments with sound, strategic guidance. The practice is co-chaired by Harrison McAvoy, who recently joined the Firm […]Steven Adler and Grant Petrosyan Co-Author Law360 Article on Spoilation
June 11, 2025
Spoliation is one of the scariest words a litigator can hear. Whether it’s your client — or worse, you — being accused of destroying or failing to preserve evidence, the consequences can be severe. And it’s not just hypothetical. Spoliation allegations have taken center stage in high-profile cases: 🔹 Charles Oakley v. MSG – Oakley’s […]