Peter Wallensteen, a leading international peace researcher, joined the Kroc Institute faculty in 2006. He spends the fall semesters in residence at Notre Dame, where he consults and collaborates with faculty on research projects, teaches a graduate seminar on international peace research, and lectures on peace research topics.

Wallensteen is a Senior Professor in the Department of Peace and Conflict Research at Sweden’s Uppsala University, where he directed the Uppsala Conflict Data Program until 2015. He continues to direct the Special Program on the Implementation of Targeted Sanctions. He was the first holder of the Dag Hammarskjöld Chair in Peace and Conflict Research (1985-2012).

He is the author of the widely used Understanding Conflict Resolution: Peace, War, and the Global System which was published in 2002, in Arabic in 2006 and in Korean in 2015. The fourth edition was published in early 2015. In late 2011 Wallensteen published Peace Research: Theory and Practice (Routledge 2011) which includes 13 previously published articles and five new essays. The book was translated into Chinese in 2014.

In 2010, Wallensteen and Isak Svensson published The Go-Between: Jan Eliasson and the Styles of Mediation (United States Institute of Peace), an analysis of one mediator's work in six crises. In 2014 Wallensteen co-edited Regional Organizations and Peacemaking: Challengers to the UN? (with Anders Bjurner, Routledge). His monograph Quality Peace: Peacebuilding, Victory and World Order is forthcoming (Oxford University Press, September 2015). The book is part of a multi-volume series on strategic peacebuilding being developed by the Kroc Institute and Oxford University Press. 

Wallensteen's interest in targeted sanctions led him to publish the edited volume International Sanctions: Between Wars and Words in 2005 (with Carina Staibano and with contributions by Kroc Institute sanctionsresearchers.) The report Making Targeted Sanctions Effective was the outcome of a large international process for improving sanctions and was presented to the UN Security Council in February 2003. The same year, Wallensteen's edited book on Nobel Peace Prize Laureate Alva Myrdal, Alva Myrdal in International Affairs, was published.

Wallensteen's other research interests include the durability of peace agreements and the impact of preventive measures on the dynamics of disputes and conflicts.