Giulio Maestro was born in Brooklyn, New York in 1942. He received a bachelor's degree in fine arts from Cooper Union in New York City. He worked in advertising for five years before becoming an illustrator. Since 1969, he has illustrated more than 125 books for young readers including numerous nonfiction books with his wife Betsy. He is also the author of a number of stories and riddle collections including The Tortoise's Tug of War. He has co-authored several books with his son Marco including What Do You Hear When Cows Sing and Other Silly Riddles and Geese Find the Missing Piece: School Time Riddle Rhymes.
Father and son riddle writers Giulio and Marco Maestro's first book together was Riddle City, USA! A Book of Geography Riddles . Their first I Can Read Book was What Do You Hear When Cows Sing? And Other Silly Riddles . The Maestros live in Old Lyme, CT.