Sendak was born in Brooklyn, to Polish Jewish immigrant parents Sadie (née Schindler) and Philip Sendak, a dressmaker. Sendak described his childhood as a "terrible situation" because of his extended family's dying in The Holocaust, which exposed him at an early age to death and the concept of mortality.

His love of books began at an early age when he developed health problems and was confined to his bed. He decided to become an illustrator after watching Walt Disney's film Fantasia at the age of twelve. One of his first professional commissions was to create window displays for the toy store F.A.O. Schwarz.

His illustrations were first published in 1947 in a textbook titled Atomics for the Millions by Dr. Maxwell Leigh Eidinoff. He spent much of the 1950s illustrating children's books written by others before beginning to write his own stories.

Sendak died in the morning of May 8, 2012, in Danbury, Connecticut, from complications of a stroke.

In its obituary, The New York Times called Sendak "the most important children’s book artist of the 20th century." Author Neil Gaiman remarked, "He was unique, grumpy, brilliant, gay, wise, magical and made the world better by creating art in it." Author R. L. Stine called Sendak's death "a sad day in children’s books and for the world."

"We are all honored to have been briefly invited into his world," remarked comedian Stephen Colbert. His final book, Bumble-Ardy, was published eight months prior to his death. A posthumous picture book is scheduled for publication in February 2013.