This qualitative study reports the mediation performed by a History teacher and aimed at developing critical multimodal literacy in students participating in a film workshop at a Chilean public school. From this theoretical-methodological perspective, the film workshop was conceived as a multimodal space comprised of curriculum macrogenres, according to Christie's conception from Educational Linguistics. Each film was considered a semiotic resource, which recontextualizes and resignifies curriculum contents. The methodology was based on the triangulation of disciplinary discourse, teaching mediation, and value construction performed in the film workshop. The results showed some strategies of teaching mediation, such as the identification of actors, processes and historical events through the pedagogy of the question, according to Freire's conception; the unpackaging and packaging of highly abstract concepts; the deployment of verbal and written verbal resources, deictic and illustrative gestures, and semiotic resources such as the map, the PowerPoint and the film itself. From the experience of this film workshop, a possible conclusion is that the History teacher weaves patterns of meaning to mediate the literacy process of the students through the mentioned strategies. In addition, the films seen during the film workshop have a significant semiotic and epistemic potential for the development of critical multimodal literacy in combination with other semiotic resources in order to create meaning in context.