Harriet Ziefert grew up in North Bergen, New Jersey, where she attended the local schools. She graduated from Smith College, then received a Masters degree in Education from New York University.
For many years, Ziefert was an elementary school teacher. She taught most grades from kindergarten to fifth grade. "I liked it," she said, but she stopped teaching when she had her own sons. When her children were older, Ziefert wanted "a bigger arena" for her work. She went to work at a publishing company, Scholastic in New York City, developing materials for teacher's guides for kindergarten language arts and social studies programs.
"About twelve years ago," says Ziefert in a 1995 interview, "I tried to get a job as an editor, but no one would hire me as a trade editor. So I decided to write my own books." Since then, she has written several hundred books, mostly picture books and easy-to-read books. "I write books very quickly," she says, "in about twelve hours. I rewrite them three times over three days, and then they're done." She writes about twenty books a year.