Duffield is also known for his philanthropic activities on behalf of animals. In 1994, Duffield and his wife, Cheryl, established Maddie's Fund, originally named the Duffield Family Foundation. In January 1999, the Board of Directors restructured the foundation, defined its mission, and adopted the current name. The organization is named after Maddie, a Miniature Schnauzer who was the Duffields' source of unconditional love and friendship for ten years, and a "lighthouse during the stormy period" of the couple's work careers. Maddie died of cancer in 1997, and Duffield acted on his earlier promise to his pet, "If we ever make some money, I promise we will give it back to you and your kind so others can be as happy as we are today."