This is an empirical study in which we explore child foreign language learners' interactional strategy use, uptake, and lexical acquisition in synchronous computer-mediated communication (SCMC). The study was carried out with 16 10-year-old Spanish English as a foreign language learners paired with age- and proficiency-matched English native speaker peers who worked together over a 5-week period on three communicative jigsaw tasks. Results show that during text-based SCMC, the children negotiated for meaning in ways that coincided with and differed from studies of young learners' face-to-face communication. Successful uptake of target lexis occurred infrequently despite high rates of negotiation, although the children's lexical knowledge improved significantly over time. Analyses of the chat scripts revealed that the learners noticed and retained additional lexical items embedded in the task and used during the interaction. They had not been the focus of negotiation, but were useful for task completion. Participation in SCMC also raised the children's awareness of gaps in their lexical knowledge and stimulated their attempts to fill those gaps outside the classroom. The results are discussed and implications suggested for implementing SCMC in instructional settings.