Although pupil mobility is a core educational activity within the process of internationalising secondary school education, only modest efforts have been made to investigate pupil mobility in upper secondary school and how to asses it. The aim of this article is twofold. First, it presents an assessment framework--the "Intercultura assessment protocol" (IAP). The IAP, which was designed through action research in the context of the Italian upper secondary school, is composed of a set of tools and follows a multimethod, multiperspective and longitudinal approach. Second, the article shows the pedagogical value of the IAP. Indeed, results suggest that some of the IAP's tools, especially those requiring deep reflection on the self and on the intercultural experience, foster pupils' self-awareness and critical thinking. These form key aspects of intercultural competence, which is one of the principal expected learning outcomes of pupil mobility.