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William J. Hammett

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Practice Areas:

  • Family Law
  • Mediator in Family Law Cases
  • Divorce
  • Paternity Actions
  • Termination of Parental Rights/Adoptions
  • Custody and Physical Placement Disputes
  • Child Support and Maintenance Actions
William J. Hammett
Rated by Super Lawyers

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William J. Hammett
Rated by Super Lawyers

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Attorney William J. Hammett is a founding member and partner with Hammett, Bellin & Oswald, LLC. Established in 1997, the law firm has offices in Neenah and Appleton, Wisconsin. Serving clients throughout the Fox Valley region and surrounding areas, Mr. Hammett represents the rights and interests of those who are going through a divorce or other serious family issue.

Attorney Hammett graduated from UW-Madison in 1986. He received his Juris Doctorate from Marquette University in 1989. Mr. Hammett is a member for the Winnebago County Bar Association and served as President in 1997-98. Mr. Hammett is licensed to practice in the State of Wisconsin and the United States District Court for the Eastern District of Wisconsin. 

Widely regarded as one of the leading family law attorneys in his region, Mr. Hammett has achieved notable success counseling and guiding client through the divorce process assisting in reaching agreements and resolving their conflicts concerning custody, placement, support, spousal maintenance, the division of the marital estate, and other related matters. Approximately 80% of Mr. Hammett's practice consists of representing clients in divorce actions, paternity actions, adoptions, and termination of parental rights proceedings. The remaining 20% of his practice consists of mediating family law disputes to help parties come to terms in the most amicable and efficient manner possible. As noted, Mr. Hammett has significant experience with paternity actions, adoptions and termination of parental rights cases. In all cases, he treats his clients with the compassion and respect they deserve as he works to help increase their chances of obtaining the favorable outcomes they seek for themselves and their children. 

Recognized for his success, Mr. Hammett holds a Martindale-Hubbell Distinguished Peer Review rating and has earned numerous other accolades from his peers. He also received many five-star reviews and heart-felt testimonials from his satisfied clients as well as 10 Best in client satisfaction award from the American Institute of Family Law Attorneys. His AVOO rating is 10. 


  • Marquette University Law School, Milwaukee, Wisconsin
    • J.D.
  • University of Wisconsin, Madison, Wisconsin
    • B.A. - 1986
    • Major: Political Science

Bar Admissions

  • Wisconsin, 1989
  • U.S. District Court Eastern District of Wisconsin, 1989

Professional Associations

  • Winnebago County Bar Association, Member, 1991 to Present
  • Winnebago County Bar Association President, 1997 to 1998

Current Employment Position

  • Partner
  • Attorney

Past Positions

  • O'Neil, Cannon & Hollman, SC, Associate, 1989 to 1991


  • Top 5% Family Law Attorneys in Wisconsin, Wisconsin Super Lawyers, 2008 - 2019
  • 10 Best Family Law Attorneys in Wisconsin, American Institute of Family Law Attorneys

Published Works

  • "Percentage Leases" Is There a Need to Imply a Covenant of Continuous Operation, Marquette Law Review, Vol 72/ No.4, 1989