This case study examines how one study abroad student oriented to social interaction during a semester in Spain. Using an activity theoretical approach, the findings indicate that the student not only viewed social interaction with his Spanish host family and an expert-Spanish-speaking age peer as an opportunity for second language (L2) learning, but also had other goals, such as relationship building and enjoyment. The analysis further highlights changes over time in the focal student's orientation to L2 learning in social interaction, with attention to the way in which his relationships mediated those shifts. Results from the study reveal the dynamic nature of social interaction, the importance of age peers, and the usefulness of activity theory for making links between micro-level interactions and macro-level social structures.