Yumi Heo was born in Korea in 1964. She received a bachelor's degree in graphic design from Sang Ji University in Korea and a MFA from the New York School of Visual Arts. The first book she illustrated was The Rabbit's Judgment, which was published in 1994. She also illustrated Henry's First-Moon Birthday by Lenore Look, Sometimes I'm Bombaloo by Rachel Vail, and Polka Dot Penguin Pottery by Lenore Look. She was the author and illustrator for several books including One Afternoon and Ten Days and Nine Nights: An Adoption Story. She died after a long battle with cancer in November 2016.