Truszczynski's research interests include knowledge representation, nonmonotonic reasoning, logic, logic programming, constraint programming and combinatorics. He is the author or co-author of over 130 technical papers. Jointly with Victor Marek he wrote a research monograph "Nonmonotonic Logic" on mathematical foundations of nonmonotonic reasoning, which marked a milestone in the development of the field. He was also a co-editor of the book "The Logic Programming Paradigm: a 25-Year Perspective", celebrating accomplishments of the field of logic programming.
Truszczynski is active in his research community. He served as organizer or program committee chair for several conferences. He is a member of the Executive Committee of the Association of Logic Programming, Steering Committee of the Knowledge Representation, Inc., and Chair of the Steering Committee of Nonmonotonic Reasoning Workshops. He also serves on editorial and advisory boards of several professional journals, including Journal of Artificial Intelligence Research, Theory and Practice of Logic Programming, and AI Communications.