Though born in New York, Champlin grew up in Toronto where he earned his bachelor's degree in modern history and master's in Classics.
He received his doctorate at Oxford, and then joined Princeton University the same year.
He taught over 40 courses during his career and wrote various books on Ancient Rome, notably a biography of Emperor Nero and studies of Cornelius Fronto and of modest Roman landowners.
His last book, Tiberius and His Age, was begun in 2007 but published in 2024, having been set aside due to illness and then finished by his colleague Robert Kaster.
[1] He was also the co-editor of The Cambridge Ancient History, 2nd edition, volume 10, The Augustan Empire, 43 B.C.–A.D.