Many of his novels are set in and around Orange County, California. As of 2006, he lives there with his wife, Gerda (Cerra), in Newport Coast, California, behind the gates of Pelican Hills. In 2008, he was the world's sixth-most highly paid author, tied with John Grisham, at $25 million annually.
In October 2008, Koontz revealed that he had adopted a new dog, Anna. Eventually, he learned that Anna was the grandniece of Trixie. Anna died on May 22, 2016. Koontz then adopted a new dog, Elsa, on July 11, 2016.