Smith is most noted for his work on bestselling and award-winning children's books. He has won the British Kate Greenaway Medal ("There Is a Tribe of Kids"), the Bratislava Golden Apple ("The Big Pets"), two American Caldecott Honors ("The Stinky Cheese Man" and "Grandpa Green"), five New York Times' Best Illustrated Book awards ("Halloween ABC", "The Stinky Cheese Man", "John, Paul, George & Ben", "Grandpa Green" and "A House That Once Was"), and lifetime achievement awards from the Carle Museum of Picture Book Art (2012), and the Society of Illustrators (2014).