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Colleen M. O'Neil

Attorney Profile

Top Rated Business Litigation Attorney in Cleveland, OH

Calfee, Halter & Griswold LLP
1405 East Sixth Street
Cleveland, OH 44114
Phone: 216-622-8530
Fax: 216-241-0816
Selected to Super Lawyers: 2012 - 2022
Selected to Rising Stars: 2009
Licensed in Ohio Since: 1996
Practice Areas: Business Litigation, General Litigation
Attorney Profile

Colleen O’Neil serves as Co-Chair of Calfee's Litigation practice group. She helps clients resolve complex business disputes.

Colleen has extensive experience in federal and state courts nationwide helping business clients resolve the following:

  • Commercial contract disputes
  • Shareholder and corporate disputes, including post-closing issues
  • Estate and probate matters
  • Trade secret claims
  • Real property disputes
  • Municipal and public law issues
  • Title VII claims

Colleen has counseled and represented businesses, financial institutions and high-net-worth individuals in a variety of corporate, commercial, fiduciary and employment disputes with a results-oriented, practical approach.  

She has successfully prosecuted and defended a variety of business tort claims in both federal and state courts nationwide.

Colleen has represented municipalities and clients in the energy industry in various types of litigation, including contractual disputes, real estate disputes and employment matters.

Colleen has been selected for inclusion to the Ohio Super Lawyers list from 2012-2021. She has also been named to the Top 50 Women Ohio Super Lawyers list from 2013-2021 and as a Top 25 Women Cleveland Super Lawyers list from 2013-2018 and 2020-2021.

She joined Calfee in 1998, and she is a member of the firm’s Practice Planning and Growth Committee and the Diversity & Inclusion Committee. Colleen began serving as Vice Chair of the firm's Litigation practice group in 2019 and Co-Chair in 2021.

About Colleen M. O'Neil

First Admitted: 1996, Ohio

Professional Webpage:


  • The Families First Coronavirus Relief Act (“FFCRA”) goes into effect on April 1, 2020, greatly expanding benefits to employees in the U.S. in these unprecedented times. We previously published information on the paid leave provisions of the FFCRA. To assist with the implementation of these emergency relief measures, the Department of Labor (“DOL”) issued on March 24, 2020 the following guidance:questions and answers regarding the FFCRA;a poster, which summarizes an employee’s rights under the FFCRA; and“Frequently Asked Questions” which provide guidance on the poster., The Families First Coronavirus Relief Act, Labor And Employment
  • On March 27, 2020, the Supreme Court of Ohio issued an order tolling the time requirements established by all rules promulgated by the Court, in light of Governor DeWine’s declaration of emergency concerning the novel coronavirus disease (COVID-19) outbreak, In re Tolling of Time Requirements Imposed by Rules Promulgated by the Supreme Court and Use of Technology2020-Ohio-1166 (“Order”). The Order works in conjunction with Am. Sub. H.B. 197, which the Governor also signed on March 27, 2020., Tolling Order Time Requirements in Light of COVID-19, Litigation

Educational Background

  • J.D., magna cum laude, Cleveland-Marshall College of Law., 1996
  • B.A. John Carroll University, 1992


  • Ohio Super Lawyer, Top 50 Female Lawyers in Ohio, Top 25 Female Lawyers in Cleveland, Ohio Super Lawyers, 2021
  • The Best Lawyers in America, Commercial Litigation, The Best Lawyers in America©, 2021
  • Woman of Professional Excellence Award, YWCA of Greater Cleveland, 2010

Bar/Professional Activity

  • Cleveland-Marshall College of Law Board of Visitors, Member, 2021
  • Irish American Law Society of Cleveland, Founding Member, Former Vice President, 2021
  • Magnificat High School, Chair, Board of Directors, May 2017 to present, 2021
  • Cleveland Marshall Law Alumni Association, Board Member, 2021
  • American Bar Association and the ABA’s Litigation Section, Member, 2021
  • Ohio Bar Association, Member, 2021
  • Cleveland Metropolitan Bar Association, Member, 2021
  • U.S. Court of Appeals for the Fifth Circuit
  • U.S. Supreme Court
  • U.S. Court of Appeals for the Eighth Circuit
  • U.S. Court of Appeals for the Sixth Circuit
  • U.S. Court of Appeals for the First Circuit
  • Supreme Court of Ohio
  • U.S. District Court for the Southern District of Ohio
  • U.S. District Court for the Northern District of Ohio
  • Ohio

Industry Groups

  • Energy And Utilities
  • Health Care
  • Private and Family-Owned Businesses
  • Public Companies
  • Real Estate.
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Office Location for Colleen M. O'Neil

1405 East Sixth Street
Cleveland, OH 44114

Last Updated: 5/15/2022

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