Sendak was the son of Polish immigrants and received his formal art training at the Art Students' League in New York City. While attending school he drew backgrounds for All-American Comics and did window displays for a toy store. The first children's books he illustrated were Marcel Ayme's The Wonderful Farm (1951) and Ruth Krauss's A Hole is to Dig (1952). Both were successful, and Sendak went on to illustrate more than 80 children's books by a number of writers including Meindert De Jong, Else Holmelund Minarik, and Randall Jarrell.

With Kenny's Window (1956), he began writing some of the stories that he illustrated. These include the tiny four-volume Nutshell Library (1962) and his innovative trilogy composed of Where the Wild Things Are (1963; winner of the 1964 Caldecott Medal), In the Night Kitchen (1970), and Outside Over There (1981). In 2006 he illustrated the pop-up book Mommy?.

In 1975 Sendak wrote and directed Really Rosie, an animated television special based on some of the children in his stories. It was expanded into a musical play in 1978. In addition to creating opera versions of some of his own stories—including Where the Wild Things Are—Sendak designed a number of other works for the stage, notably the city of Houston's production of Mozart's Magic Flute in 1980. In 1983 he designed a production of Tchaikovsky's ballet The Nutcracker for the Seattle (Wash.) Ballet. He published Caldecott & Co.: Notes on Books and Pictures, a collection of essays and reviews on writers and illustrators, in 1988. He was awarded the National Medal of Arts in 1996.

The Art of Maurice Sendak by Selma G. Lanes was published in 1980.