Gregory S. Mager

Attorney in Milwaukee, WI
Gregory assists his clients with family law matters. He uses his extensive skill, training, and experience in collaboration, negotiation, and litigation to help his clients achieve successful resolutions of their divorce, paternity, custody, placement, and support matters. Gregory is a Fellow in the American Academy of Matrimonial Lawyers and an active member of the Collaborative Family Law Council of Wisconsin. He is a member of the Divorce Cooperation Institute and is recognized by judges and peers as one of Wisconsin’s premier family law attorneys. He is uniquely positioned to successfully represent clients in their family law matters, including those involving complex business, financial, and child-related issues. His approach will produce the best results for the client and the client’s family, whether through litigation, mediation, or collaborative divorce.

• Divorce
• Collaborative Divorce
• Cooperative Divorce
• Paternity
• Custody and Placement
• Support
• Post-judgment Matters
• Mediation
• Appellate Matters

• Estate of Laubenheimer, 2013 WI 76, 350 Wis. 2d 182, 883 N.W.2d 735
• Lyman v. Lyman, 2011 WI App 24, 331 Wis. 2d 650, 795 N.W.2d 475

• Named one of "Milwaukee's Leading Lawyers" by M Magazine in Family, July 2014 issue; Divorce/Separation, July 2013 issue; and in Divorce and Family, July 2012 issue. Only 2-5% of the top ranked attorneys published by Avvo for each category were recognized.
• Selected for inclusion in Wisconsin Super Lawyers, Law & Politics and Milwaukee Magazine, December 2013
• Fellow, American Academy of Matrimonial Lawyers (2012–).
• Martindale-Hubbell® Peer Review Rating™–AV Preeminent, reflecting an attorney who has reached the height of professional excellence and is recognized for the highest levels of skill and integrity.
• He has been given a rating of 10.0 (out of a possible 10.0) by Avvo, a national attorney rating service which uses a mathematical model to rate attorneys based on experience, professional achievements, industry recognition and professional conduct.
• Selected for inclusion in Wisconsin Super Lawyers Rising Stars, Law & Politics and Milwaukee Magazine, December 2007, 2009, and 2010 issues
• 2004- 2005 American Bar Association Section of Family Law Chair's Award, "For meritorious service exceeding what is expected of our leadership."

• Training Committee, Collaborative Family Law Council of Wisconsin, Inc. (2014–)
• State Bar of Wisconsin, Family Law Section, Board of Directors (July 2010–July 2013, July 2013–)
• Editor in Chief, Wisconsin Journal of Family Law (2007–2008)
• Member, American Bar Association Section of Family Law CLE Committee (2005–2006)
• Vice-Chair, American Bar Association Section of Family Law Trial Practice and Techniques Committee (2001–2004, 2005–2006)
• Chair, American Bar Association Section of Family Law Trial Practice and Techniques Committee (2004–2005)
• Vice-Chair, American Bar Association Section of Family Law CLE Committee (2004–2005)
• Vice-Chair, American Bar Association Section of Family Law Bankruptcy Committee (2003–2004)
• Court Commissioner, Milwaukee County Circuit Court, Appointed by Hon. Diane S. Sykes (1998)

• Speaker, O’Neil, Cannon, Hollman, DeJong & Laing, 2014 Hot Topics for Small Firm and Solo Practitioners seminar, “Issues Relating to Recent Developments in the Legal Profession”

American Academy of Matrimonial Lawyers—Wisconsin Chapter

• Speaker: “Hot Tips: Double Counting Reminders” (March 2013)

Society of Financial Service Professionals
• “Financial Planning for a Second Marriage” (March 2012)

American Bar Association Section of Family Law
• Co-Producer: “Executive Compensation: Is it Income or is it Property?” (May, 2006)
• Co-Producer and Moderator: “Direct Examination of the Financial Expert: How to Make Your Point and Not Lose Your Audience” (September, 2005)
• Co-Producer and Moderator: “Hot Tips from the Experts” (August, 2005)
• Speaker: “Allocation of Dependency Exemptions in Paternity Case and Other Tax Tips” (August, 2004)
• Producer and Moderator: “Challenging the Superego: How to Prepare for a Psychologist's Testimony” (April, 2004)
• Co-Producer and Moderator: “Preparing and Presenting Domestic Violence Protective Order Cases” (May, 2003)
• Co-Producer and Moderator: “Ethics at Trial in Spite of Your Client” (October, 2003)

State Bar of Wisconsin Family Law Section
• Civil Procedure, Evidence, and Pretrial Discovery, Family Law Workshop (August, 2014)
Temporary Hearings—A Panel Discussion, Family Law Workshop (August, 2014)
• Child Related Financial Issues, Property Division Maintenance, Family Law Workshop (August, 2013)
• Literature Review, Family Law Workshop (August, 2000)
• Case Law Update, Annual Convention (June, 1999)

Law Education Institute, Inc., National CLE Conference®, Family Law Program
• “The Rules of Evidence: They DO Apply In Family Law” (January, 2004)
• “What Effective Negotiators Bring to the Table” (January, 2003)
• “Tricks of the Trade: Low Budget Computer Applications” (January, 2002)
• “Using a Psychologist as a Consulting Expert: Preparing Your Client for the Inevitable” (January, 2001)
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Peer Rating 5.0 of 5

Areas of Law

  • Family Law
  • Civil Litigation
  • Mediation
  • Appellate Practice


Peer Rating


Overall Peer Rating

5.0 out of 5.0
  • Meets very high criteria of general ethical standards
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Experience & Credentials



Admission Details

Admitted in 1997, Wisconsin and U.S. District Court, Eastern District of Wisconsin

Credit Cards Accepted
Additional Payment Information
  • Fixed Hourly Rates
  • Fixed Fees Available
  • Law School Attended

    Marquette University
    Class of 1997

    University Attended

    Marquette University
    Class of 1992
    Political Science and Philosophy

    Marquette University
    Class of 1994
    Political Science

    Associations & Memberships

    •Milwaukee, Waukesha and Ozaukee County Bar Associations;
    •State Bar of Wisconsin;
    •American Bar Association;
    •Society of Family Lawyers,
    •Col... More

    Contact Information


    414-276-5000 Call Now




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    Office Information
    Gregory S. Mager
     111 East Wisconsin Avenue, Suite 1400,
    Milwaukee, WI 53202-4870


    O'Neil, Cannon, Hollman, DeJong & Laing S.C. (Milwaukee, Wisconsin)

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