Justin Smith grew up in New York City and attended the Bronx High School of Science and Hunter College. After earning his Ph. D. in Mathematics from New York University, he held teaching positions at Rice University, the University of Hawaii, and SUNY, before becoming a professor of Mathematics and Computer Science at Drexel University.

He is currently a Professor Emeritus of Drexel University.

He lives in a suburb of Philadelphia with his wife Brigitte and their three cats, Rusty and Gerri, and Shadow.