While humour is recognised as an influential resource in language teaching, systematic discourse-based research on how humorous actions shape interactional dynamics in multilingual classrooms—and how teachers respond to humour in students’ heritage languages—remains limited. This study addresses this gap through a qualitative corpus-pragmatic analysis of thirty-three ApaeK corpus transcripts from German L2 classrooms. In addition, ten supplementary interviews with students and teachers were analysed to contextualise and enrich the corpus findings. Using Goffman’s frame analysis and conversation analysis, humorous actions were identified through iterative coding that triangulated semantic incongruity, laughter annotations, sequential positioning, and contextual transcript notes. The analysis shows that irony, playful teasing, and sarcasm were the most frequent humour types observed. Humorous actions often functioned as frame disruptions that prompted teacher reframing efforts such as rule impositions or prohibitions. Humour in students’ heritage languages was disproportionately likely to elicit corrective responses, although the data provide no evidence that such humour was intentionally disruptive. Teachers’ reactions were frequently influenced by comprehension gaps or stereotype-based insecurity rather than student intent. The study operationalises humour competence as the ability to recognise frame disruptions, interpret interlocutor intent, and respond constructively across L1 and L2 contexts. Limitations include the absence of audio/ video data and the qualitative scope of the sample. The inclusion of the ten interviews enhances triangulation but remains limited in number, highlighting the exploratory nature of the findings. Future research should incorporate multimodal corpora and evaluate training interventions to foster humour competence. By clarifying interactional patterns, teacher responses, and institutional implications, this study enhances empirical understanding of humour’s role in multilingual German L2 education and informs teacher development for more inclusive practice.