Classroom interpersonal dynamics play a key role in shaping the interactional profiles of language learners and the development of their speaking skills. However, it can be challenging for learners to navigate social interactions with classmates, especially if they lack confidence in their L2 self. This is especially true for first-year undergraduates in Japan who often struggle to adapt to unfamiliar communicative language lessons taught in the target language. King’s (2013) examination of learner silence established a connection between low oral participation, anxiety, and social inhibition. In some cases, however, silence is not just a non-verbal cue of speaking-related anxiety (Maher & King, 2020); it can also be a contributing factor to avoiding talk. Using King’s (2014) cognitive-behavioural model of silent L2 learners’ anxiety, this paper examines how ‘silence’ can trigger speaking-related anxiety in Japanese university English-medium classrooms. The study used a cognitive-behavioural theory (CBT)-based approach to gain insights into students’ perceptions of their in-class behaviours. Forty-five semi-structured interviews were conducted with 17 participants using an interview schedule based on a CBT formulation to explore students’ silent behaviour, associated thoughts and feelings, and behavioural triggers. Multiple recurrent forms of classroom ‘silence’ reported by the participants included using Japanese when English was expected, finishing speaking turns quickly, and taking on the listener role rather than initiating discourse. The findings reveal ‘silence’ as a trigger of speaking-related anxiety. The discomfort some participants felt during a display of ‘silence’ seemed to trigger a fear of being negatively evaluated by classmates, leading to self-doubt about their language proficiency and social performance. These findings contribute further insights into the causes of speaking-related anxiety and learner ‘silence’. Our study points towards using CBT-based approaches to improve speaking confidence by increasing learners’ awareness of their anxiety triggers.</p