This article deals with internationalization in the field of higher education, focusing on the impact of transnational academic mobility on the university communities. Drawing on the results of a qualitative research study at different departments in a Norwegian university, this article explores the interaction between transnational academics and their Norwegian counterparts in an academic professional community. The key questions are the impact of internationalization on the working day at the departmental level, and how academics themselves experience working together with colleagues from all over the world. The topics are presented in the following four themes: informal interaction, cooperation, language practices, and internationalization. In the light of data gained through observation and informal dialogs in two departments that collectively consisted of 108 academic staff members, and formal interviews with 34 of them, both transnational and national, the paper concludes that the academics regard internationalization as a great source of professional knowledge. However, considerable institutional and personal adjustment is required to fully exploit the professional potential of diversity among the academic staff.