The daughter of historian Frederick Hill Meserve, she was married to Philip B. Kunhardt, Sr. They had four children: Nancy Kunhardt Lodge, Philip B. Kunhardt, Jr., Kenneth Kunhardt, and Edith Kunhardt. She is the grandmother of Peter Kunhardt. Philip Jr. authored The Dreaming Game,a biography of his mother.

Kunhardt wrote nearly 50 books, including one of the bestselling children's books of all time, Pat the Bunny, which has sold over six million copies. Other works include the well known Twenty Days, an account of Lincoln's assassination and the twenty days that followed, which she wrote with her son, Philip B. Kunhardt, Jr.; Tiny Animal Stories; The Telephone Book; Lucky Mrs. Ticklefeather; Brave Mr. Buckingham; Junket is Nice (1933); Wise Old Aard-Vark (1936); and Now Open the Box.