He obtained his B.A. in English from Harvard University where he graduated Magna cum laude. He later received his Ph.D. in medieval history from the Yale University. His thesis was The Influence of Joachim of Fiore on the Early Franciscans: A Study of the Commentary Super Hieremiam. He also received a Diploma in Latin Letters from Gregorian University in Rome.
Moynihan is founder and editor-in-chief of the Inside the Vatican. He frequently speaks on Catholic issues and has appeared on a number of media outlets which include: Fox News, CNN, ABC, EWTN and many others.