About Dennis
Dennis Duncan is a attorney based in Sioux Falls, South Dakota, specializing in business and health care law. He has been practicing law in South Dakota since 1973, following his graduation from the University of South Dakota School of Law. Over the years, Dennis is known for his expertise in business contracts, mergers and acquisitions, and health care regulations. He is admitted to practice in the state of South Dakota and is a member of the South Dakota State Bar Association. In 2018, Dennis co-founded The Duncan Law Firm, LLP, located at 515 W.
Landscape Place, Suite 101, Sioux Falls, SD 57108. The firm focuses on government relations, lobbying, and legislative affairs, offering a team-based approach to client representation. Prior to this, he was a partner at Zimmer, Duncan & Cole, LLP, from June 1974 to December 2017. His experience includes serving as a law clerk to the Honorable Frances Dunn, Justice of the South Dakota Supreme Court. Dennis has been recognized for his contributions to the legal field, being selected to Super Lawyers from 2011 to 2025.
His professional associations include the South Dakota State Bar Association, the American Bar Association, and the National Health Lawyers Association. He has also been involved in various committees, such as the Supreme Court-appointed study committee on the bar admissions process in 2022. Throughout his career, Dennis has been actively involved in legislative matters, representing clients in lobbying and government relations. His firm, The Duncan Law Firm, has achieved its status as a premier government relations firm through its use of a team approach to client representation. Team members are kept current on the status of client legislation and, at critical junctures, join in an “all-out” lobbying effort.
This team approach enables the firm to lobby whole committees and the entire membership of the legislature in the critical hours or minutes while legislation is considered. Dennis's commitment to the legal profession and his community is evident through his active participation in various professional organizations and his dedication to providing quality legal services to his clients. His experience and involvement in legislative affairs make him a valuable resource for clients seeking expertise in business and health care law.
