Alexander Thomas was a social and organizational psychologist and one of the best-known German interculturalists, whose work significantly shaped German intercultural research and practice. He is considered one of the few representatives of intercultural psychology. His research approach is applied and practical. He understands culture as a symbolic system of orientation that serves to solve problems. With his cultural standard model, Thomas has made an important contribution to the analysis of intercultural situations. His research on intercultural action competence and its developmental stages have also enriched academia. Thomas’ research focused on the psychology of action, comparative cultural psychology, the psychology of intercultural action, and organizational psychology.