Marc Simont was born in Paris in the year 1915. His parents were from the Spanish province of Catalonia, and he spent his boyhood in France, Spain, and the United States. Simont considers his father to be his greatest instructor, despite later attending art school in Paris and New York. When he was nineteen, Simont moved to America permanently, aiming to support himself as an artist. In 1939, he created his first pictures for a children's book.

Simont has worked with authors as different as Margaret Wise Brown and James Thurber on roughly a hundred novels since then. Marc Simont's art is in collections all over the world, including the Kijo Picture Book Museum in Japan, where he won a Caldecott Honor in 1950 for illustrating Ruth Krauss's The Good Day, and the Caldecott Medal in 1957 for his illustrations in Janice May Udry's A Tree is Lovely. Marc Simont's art is in collections all over the world, including the Kijo Picture Book Museum in Japan. Simont has a grown son, two dogs, and a cat with his wife. They live in the Connecticut town of West Cornwall.

The Stray Dog is Marc Simont's most recent book.