Dennis Leon Arfmann
January/February 2026
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Dennis Leon Arfmann
February 12, 1951–October 21, 2025
Dennis Leon Arfmann, age 74, of Boulder, passed on October 21, 2025, at his residence. He was born on February 12, 1951, in Neola, Iowa, a son of the late Leon and Vonda Arfmann.
Dennis practiced law for over 30 years in Colorado. His true passion during his career was his work in environmental law. He worked to spread this passion by serving as senior policy advisor for the Center for a New Energy Economy at Colorado State University and serving on several nonprofits, including Bridge House, the Earth Day Network, the Denver Regional Air Quality Commission, and the American Lung Association of Colorado. During his time as a partner at Hogan Lovells, he co-chaired the firm’s Global Climate Change and Clean Energy Group. Dennis was also heavily involved in politics and greatly enjoyed a good debate and challenging others’ positions.
Over his life, Dennis had many different passionate pursuits—tennis, the law, running, poetry, pickleball—but for him, the heart of living was the friendships he formed wherever he went. This is a skill he learned from his parents. In Neola, where he was born, he was the most popular player on the Volunteer Fire Department Little League Team. In Ralston, Nebraska, where he attended high school, he formed lifelong friendships with his classmates and neighbors—the 80th Street Crew. In Scottsbluff, Nebraska, where he first practiced law, he was a founding member of the Platte River Yacht Club. And later in life, in Boulder, the Paisanos Book Club was a deep source of companionship, joy, and laughter.
Dennis was preceded in death by his younger brother, Rick Edward Arfmann. He is survived by his wife, Julie Brown; his two children, Sara and Ben; his brother Bill; his nephew, Josh; his niece, Adriana; and his cousins, Bonnie, Heather, Mike, Doug, Marty, Greg, and Matt.
Memorial contributions may be directed to the Tisch Brain Tumor Center or the Panhandle Humane Society, two organizations that Dennis loved and championed in his life.
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