Avi was born in Manhattan on December 23rd, along with his twin sister. He had a learning disability, which made writing difficult, but a love of reading, storytelling, and a tutor made him want to write, which he eventually did after his children were born.
A graduate of the University of Wisconsin and Columbia University, with a master's degree in library science, Avi's first book was Things That Sometimes Happen, published in 1970. When asked if he has another name, he replies "The fact is, Avi is the only name I use." He received a Newbery Honor for The True Confessions of Charlotte Doyle. In 2003, he was awarded a Newbery Medal for Crispin: the Cross of Lead. Avi and his wife live in Rhode Island.