This article discusses the benefits of employing Grounded Theory Methodology (GTM) in international comparative studies from a methodological point of view. After a short introduction to the main characteristics of GTM, the article focuses on three methodological issues concerning GTM and comparative studies: First, the question of case selection and theoretical sampling, second, the parallels of the constant comparative method and comparison as a method, and third, the concepts of tertium comparationis and core category. All three aspects are discussed in relation to a study on Swedish and German teachers’ justice beliefs regarding assessment in school. GTM, it is argued, is a tool to face well-known challenges of comparative research, such as methodological nationalism, thereby contributing to ongoing discussions about relating methodological principles of qualitative research to comparative research.