This study analyses interactions between pairs of children (aged 4-5) together with their teacher during digital storytelling activities in preschool to explore how children express and negotiate their agency and how teachers respond to it. Theoretically, agency is understood as relational and situated meaning that it stems from, and it is shaped by participation in interactions in specific sociocultural settings. Data include 140 h of video recordings in which participants (10 children and 2 teachers) recreate a familiar story using the application Book Creator. The findings show that, even in these activities that were designed by the researcher and the teachers and had a preliminary framework, children expressed their agency by altering the story plot, negotiating the meaning of their drawings with peers, and exploring the design characteristics of the digital tablets. The teachers and digital tables (including the application) mediated the dynamic process of children's agency. The study concludes by emphasizing a responsive teaching approach that opens up for and encourages children's agency.