This chapter reports on the design and implementation of a concept-based instruction (CBI) intervention for teaching the concept of (im)politeness to Danish university students learning Spanish as L2. Situated within the Vygotskian framework of sociocultural theory (SCT), this chapter analyzes one student’s emergent understandings of the concept of (im)politeness as a situated phenomenon and provides insights into how this concept mediates the student’s thinking in the process of understanding the social and cultural norms that underlie verbal interaction. The student’s reflections show how the concept of (im)politeness is used to shape her understanding of communicative interaction related to the content of face in Spanish social relations and to her own social identity as an L2 speaker.