John O'Byrne held degrees from Syracuse and Harvard. He was a member of the faculty at University of Iowa College of Law from 1948 to 1966, specializing in tax law. He helped create the Iowa Law School Foundation in 1952, as well as the Agricultural Law Center in 1953.
After leaving Iowa, he served as a dean and professor at Northwestern University from 1966 to to 1977. In 1977, he joined the faculty at University of Georgia School of Law, where he spent the rest of his career. After his death in 1989, University of Georgia established the John O'Byrne Memorial Faculty Award, recognizing faculty who provide outstanding guidance to students.