Born in in 1896 (note: some sources say 1899), in the Austro-Hungarian Empire, she served as a nurse during World War I. Kate Seredy's father, Louis Peter, was a teacher.She moved from Budapest to the United States in 1922, with an art teacher's diploma from Academy of Arts, Budapest. In 1935, she published her first book, The Good Master. Many more were to follow, although she always considered herself an illustrator before an author. She illustrated her work in her own unique style and her books were "an excuse for making pictures" . Her 1937 novel, The White Stag was awarded the Newbery Medal for excellence in children's literature.

She lived at Montgomery, New York.Her hobbies included "woodcarving, sculpture, making pottery, painting children's portraits, and designing and sewing" .

She died of heart failure on March 7, 1975 at the age of 78.