Born in Brooklyn, Marcellino began as an abstract expressionist painter and spent 1963 studying in Venice on a Fulbright Scholarship.

Marcellino, however, insisted on reading the entire manuscript and producing a carefully designed, tasteful illustration that captured the overall mood of the book, often symbolically.

Art director Steven Heller described Marcellino's approach: In the mid-1980s, he began doing children's books, starting with Tor Seidler's A Rat's Tale.

He found it to be a different experience, commenting: Charles Perrault's Puss in Boots, his first full-color picture book, won a 1991 Caldecott Medal, and he won more awards with The Steadfast Tin Soldier, The Wainscott Weasel, The Pelican Chorus and Other Nonsense, The Story of Little Babaji (a revision of The Story of Little Black Sambo) and Ouch!

In December 2016, it was announced that Arrivederci, Crocodile would be completed by the French illustrator Eric Puybaret and published in September 2019 by Atheneum.