Though born in Orange County, New Jersey on April 3, 1953, Sandra Boynton was raised in Philadelphia, Pennsylvania. The third child to parents Robert and Jeanne, Boynton was raised as a Quaker and attended Germantown Friends School, where her father taught English.

She attended Yale, where she studied English. The summer of her junior year, she began creating gift cards, which she printed in her uncle's press and sold to stores. Perhaps the key to Boynton's success was her mastery of a new style of greeting cards—a style that avoided sentimentality and clich?? and instead delivered humor, whimsy, and wit. Her best-selling greeting cards feature whimsical cartoons such as a hippo, dinosaur, and pig. These memorable characters have appeared on thousands of cards over the years, as well as novelty items like mugs and calendars.

After Yale, Boynton attended the University of California, Berkeley, where she studied drama. While there, she continued designing greeting cards, later signing with a Chicago company, Recycled Paper Greetings. After a year at Berkeley, Boynton transferred to Yale to study drama, but later dropped out. It was there that she met her husband, Jamie McEwan.

While in the greeting card business, Boynton wrote children's books on the side. Her first book, Hippos Go Berserk, was written in 1977 while still a student at Yale. It is in this first book that readers witness her fine ear for nonsense rhyme; the book is both visually entertaining and a counting book for children, and was described by a writer for Wilson Library Bulletin as "light, airy, and tender." The same year, she published Hester in the Wild and Gopher Baroque and Other Beastly Conceits.

Since then, Boynton has written numerous children's books, focusing on her unforgettable hippo, pig, cat, turkey, and dinosaur characters--all of which have human attributes. When questioned as to why she she does not directly represent people, Boynton claimed she cannot draw them as well as animals. She also noted benefits of depicting animals: "[U]sing [animals], an artist becomes largely freed from the constraints of age, gender, race, and so on, Boynton explained to Simon & Schuster.

Boynton's talent is not limited to children's books; she has also written a handful of adult books, such as Chocolate: The Consuming Passion, which was motivated, she says, by her allure to have all of her chocolate expenses as tax-deductible. This novel graced the New York Times bestseller list for 24 weeks in 1982. She has released multiple collections of children's songs: Rhinoceros Tap: And Fourteen Other Seriously Silly Songs; Philadelphia Chickens, which includes songs about dancing wacky animals; Dog Train; Blue Moo: 17 Jukebox Hits From Way Back Never. Philadelphia Chickens was nominated for a Grammy Award in 2004, for best musical album for children.

An illustrator and author with multiple titles to her credit, Boynton shows no signs of slowing her pace. In the late 1990s Boynton stopped creating new greeting cards, though her classic designs remained available; she is, however, focusing more attention to children's books and songbooks. Boynton currently lives in New York City with her husband and two children, where she continues creating memorable stories with lovable characters.