The research presented here is an examination of how child language novices (zero beginners) develop interactional competences and repertoires in a Swedish as a second language classroom. Two 7-year-old girls’ learning trajectories are the focus in a yearlong study of their second language (L2) development. The girls’ transition from highly repetitious and formulaic production to formally and semantically more diverse discourse is documented, along with a broadening of the girls’ classroom interactional repertoires. They initiated and took part in interactions with teachers and peers and participated in a growing range of classroom discursive activities. The longitudinal analysis also documents the differences in their two learning trajectories, particularly in terms of their L2 resources and pragmatic skills, as well as their identities as successful or unsuccessful language learners (as ascribed to them by the teachers). The study illustrates an intricate and synergistic, rather than unidirectional, relationship between these two child novice learners’ competences, L2 features, and identities.