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Mark C. Nielsen

Washington, DC

Trusted employment attorney serving Washington.

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Mark C. Nielsen is an attorney based in Washington, DISTRICT OF COLUMBIA. The practice focuses on Employment and Litigation.

Based in
Washington, DISTRICT OF COLUMBIA
Experience
attorney
Known for
Employment · Litigation
  • Handles Employment and Litigation matters from Washington, DISTRICT OF COLUMBIA.
  • Recognized with Best Lawyers in America — Litigation - ERISA (2026).

About Mark C. Nielsen: Mark C. Nielsen is an attorney based in Washington, DISTRICT OF COLUMBIA. The practice focuses on Employment and Litigation.

Areas of practice

Practice focus

Mark C. Nielsen represents clients in Washington, District of Columbia across the following areas of law. Each area links to other verified attorneys with the same focus.

Biography

About Mark C. Nielsen

Mark’s background includes a broad array of multijurisdictional and complex commercial disputes, including class action litigation.

He has practiced before state and federal courts, as well as in arbitration actions, and he has been involved in all aspects of litigation—from pretrial discovery and motion practice to trial advocacy and appellate practice. He regularly represents plans, their sponsors, and insurance companies before federal and state regulatory agencies.

As a litigator, he has successfully defended plan trustees and plan sponsors in federal court against breach of fiduciary duty and prohibited transaction claims brought by the Department of Labor and plan participants and beneficiaries. These claims involved complex commercial real estate developments, stock option and stock repurchase programs, and multiple employer welfare arrangements. He has also successfully defended plans and their fiduciaries in benefit claim disputes in both trial and appellate courts, and he has successfully defended employers against claims arising under the Americans with Disability Act.

In addition, Mark regularly counsels plans, plan trustees, and plan sponsors as to their fiduciary obligations under ERISA. These include duties attendant to plan investments and transactions, as well as the requirements of federal and state health care laws, including Medicare Part D, HIPAA, COBRA, and the Age Discrimination in Employment Act.

Mark previously served as a member of the firm’s Executive Committee.

Credentials

Education

  • New York University

    J.D. · 1997

Recognition

Awards & honors

  • Best Lawyers in America — Litigation - ERISA

    2026

  • Best Lawyers in America — Additional Areas of Practice:

    2026

  • Best Lawyers in America — Employee Benefits (ERISA) Law

    2026

Locations

Office locations

Main office

1701 Pennsylvania Avenue, NW

Washington, District of Columbia 20006

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Client reviews

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Frequently asked

Common questions

  • What areas of law does Mark C. Nielsen practice?

    Mark C. Nielsen focuses on Employment and Litigation.

  • Where is Mark C. Nielsen located?

    Mark C. Nielsen primarily serves clients in Washington, District of Columbia, with an office at 1701 Pennsylvania Avenue, NW.

  • Is Mark C. Nielsen a verified attorney?

    Mark C. Nielsen's profile is listed but has not yet been claimed by the attorney. Verification status is pending.

  • How can I schedule a consultation with Mark C. Nielsen?

    You can book a consultation through LawyersListed directly from this page. Initial outreach can also be made by phone at 202-857-0620.