<p>The study investigates how lecture slides shape real-time (non)comprehension during EMI university lectures. While slides incorporate multiple modes of discipline-specific semiotic resources, they are often treated as a supportive tool in EMI classrooms. Moreover, how students perceive and use slides during lectures to construct meaning in real time has rarely been examined. Fifteen students in four different disciplines used a footpedal device to mark moments of comprehension challenges during the lectures at a university in Sweden. The reasons for these challenges were then collected using a video-based stimulated recall interview. Corresponding slides and lecture recordings were used to specify the slide-related comprehension issues, and were categorized using a thematic analysis. Findings demonstrate that text and image content, and misalignment between slides and lecture frequently cause comprehension difficulties. At the same time, issues were often interconnected and highly individualized. The findings expand the notion of multimodality in the classroom to include “time” and “note-taking”, which have received limited attention in prior slide-related research. The study suggests that composing, using, and understanding slides is part of disciplinary literacy: a community of practice that requires students to be socialized into.</p>