Studies investigating repetition in SL/FL learners' private speech have focused mainly on its cognitive and metacognitive functions. In the present study, the classroom observations, video-recordings of lessons, audio-recordings of six learners and two teachers and simulated recall interviews were conducted in Japanese language classes over two semesters. Repetition was found to have not only cognitive and metacognitive functions such as processing and monitoring, but also social and affective functions such as increasing learners' involvement and enjoyment. Repetition appears to promote learners' participation in both classroom and conversational situations.