This study investigates the nature of teacher-child interaction and teacher scaffolding in Finnish second language (L2) classrooms. Although previous research on classroom interaction has highlighted the importance of scaffolding in language learning, much less is known about the importance of scaffolding for younger children's L2 learning. Utilising a sociocultural approach, this study aims to fill this gap. The data were collected from seven pre-primary/early primary L2 classrooms, with four teachers and 205 children through video recording (56 h) and observational field notes. The interaction analysis focused on the communicative functions of teacher-child interaction, teacher and student initiations, and teachers' scaffolding children's participation during whole-class and small-group sessions. The results show how teacher-child interaction during small-group sessions supported the children's active participation in L2 interaction and learning. The results also suggest how changing from teacher-centred modes of classroom interaction to child-centred and playful interaction is challenging and requires strong teacher professionalism.