Betsy Lewin grew up in Clearfield, Pennsylvania. She always loved to draw and can't remember ever wanting to be anything but an artist. Her mother (a kindergarten teacher) is responsible for her love of children's books. She read to Betsy and her brother every night: Winnie the Pooh, The Adventures of Barbar, Uncle Remus and all the fairy-tale books. The illustrators Ernest Shepard and A. B. Frost were among her earliest heros. Later on, when she started illustrating for children, Betsy realized how strongly she'd been influenced by the gentle watercolors of Beatrix Potter and the energetic line and humor of James Stevenson and Quentin Blake.
After graduating from Pratt Institute, where she studied illustration, Betsy took a job as an assistant art director at a greeting card company in New York, which lead to freelance work for several other card companies. Then she began to write and illustrate stories for children's magazines. When an editor at Dodd, Mead and Company asked her to expand one of those stories into a picture book, Betsy says, "I jumped at the chance. I've been doing picture books ever since and loving every moment."