The aim of this study was to examine how different types of interactions (interaction and intra-action) and the use of written language can impact in learning key expressions through learner-led activities. Four learner-led activities were designed to encourage interaction among elementary school students, which were then implemented on 5th grade students. The study recorded the students’ interaction patterns, and conducted pre- and post-tests to analyze the effects of interaction types and written language use on fluency, accuracy, and linguistic knowledge related to key expressions for the activities. The main findings indicate that interaction was more effective in enhancing the learning of key expressions, with a larger effect size. Additionally, the use of written language was found to be more effective in promoting the learning of key expressions, also with a larger effect size. These results offer valuable insights for designing learner-led activities that emphasize interaction among learners.