From 2004 to 2011, he also held the title of Distinguished Professor of Medieval History Emeritus at the University of California, Los Angeles.

[3] Raised in Louisiana, Geary was educated at Spring Hill College in Mobile, Alabama, and the Catholic University of Leuven in Belgium.

Geary's primary area of research has been in the early Middle Ages, from circa AD 500 to circa 1100 His scholarship has made significant contributions to a number of areas of medieval social and cultural history, including the cult of relics, literacy and social memory, conflict and dispute resolution, and the formation of ethnic identity in early Europe.

[4] At UCLA from 2005 to 2012, Geary directed a multi-year, international collaborative project sponsored by the Andrew W. Mellon Foundation to produce a computerized image and object database of the Plan of Saint Gall, a medieval architectural drawing of a monastic compound dating from the early ninth century.

[5] At the Institute for Advanced Study, Geary worked with an interdisciplinary team of North American and European researchers to apply advanced DNA analysis to early medieval burial remains from Italy and central Europe to help understand population movement and social structures during the so-called "barbarian migrations".