Justin Leidwanger's research and fieldwork focus primarily on the role of socioeconomic networks in ancient Mediterranean life. These interests lead him to spend time in and around the Mediterranean's waters, where his fieldwork explores the shipwrecks, ports, and ceramics that provide primary archaeological evidence for mechanisms of communication and exchange spanning the Hellenistic era through Late Antiquity.
In 2012, he initiated the Marzamemi Maritime Heritage Project, which combines archaeology with heritage management and development in southeast Sicily. The first archaeological focus has been on excavation, preservation, reconstruction, and research related to the famous 6th-c. Marzamemi “church wreck,” which sank while carrying a massive cargo of prefabricated marble architectural elements. This work has since expanded and transformed into Project 'U Mari, which explores the diverse but interrelated facets of maritime connections in this corner of the Mediterranean, from colonization and trade to warfare and the refugee crisis. Building on surveys along this coast, his larger collaborative project now under development focuses on the social and economic worlds of 2500 years of tuna fishing using maritime landscape archaeology at the port of Vendicari and documentation of fading material culture and knowledge associated with the traditional mattanza. He has been involved in shipwreck surveys off various coasts of Turkey and Cyprus since 2003, and between 2011 and 2015 co-directed investigations at the ancient port of Burgaz, along southwest Turkey's Datça/Knidos peninsula.
As a Fellow of the Penn Cultural Heritage Center, he has been involved in diverse public engagement, issues of ethical stewardship, and innovative strategies for incorporating maritime cultural heritage into economic and coastal development. He teaches courses and advises students on topics in Roman archaeology, trade and the ancient economy, networks and connectivity, Mediterranean ports, ceramic production and exchange, Greco-Roman architecture and engineering, and archaeological ethics. His lab at the Archaeology Center serves as a research base for field projects as well as a center for digital modeling (structured light scanning, laser scanning, photogrammetry, GIS, network analysis) and pottery analysis (petrography, pXRF).