Abstract Research in Content and Language Integrated Learning (CLIL) is beginning to examine learners’ development of bi-/multilingual disciplinary literacies (BMDLs). Digital technologies play a key role in this process, yet little is known about how teachers integrate them in CLIL mathematics classrooms. This article presents a comparative case study of two secondary mathematics teachers: one in an English-medium school in Spain, the other in an Irish-medium school in Ireland. Data were generated through semi-structured interviews and resource-stimulated recall sessions, and analyzed thematically within and across cases. Findings show that tools like Desmos, GeoGebra, GimKit, and Quizlet supported distinct literacies — procedural, graphical, modeling, and terminological — but their effectiveness depended on teachers’ technological pedagogical content and language knowledge (TPCALK). While digital tools increased engagement and multimodal reasoning, their monolingual design constrained bilingual scaffolding. The study concludes that BMDL-sensitive design and explicit attention to language are essential in CLIL mathematics pedagogy and recommends further classroom-based research.
