Karol Madaj graduated in biblical theology from the Catholic University of Lublin. For 11 years (2008–19), he was employed at the National Education Office of the Institute of National Remembrance, and was involved in the establishment of the Centre for Historical Education in Łódź and then served as acting head of the Department of Historical Education.
In 2019–20 he worked for the Pilecki Institute – Center for Totalitarian Studies, as a consultant and undertaking research mainly for the ‘Called by Name’ project. He co-created the Pilecki Family Museum in Ostrów Mazowiecka and was its director (2020–3). In 2023 he became the head of the Polish History Museum’s Centre for Information and Education on Poles rescuing Jews under German occupation. Since September 2025 he has been the acting director of the Pilecki Institute.
He is a widely published author of 20th-century history, including the educational board game Queue (2011) among 40 other games.