This longitudinal case study explores how students' epistemic uncertainty in argumentation can be adapted as a resource to develop knowledge in a fifth-grade classroom. Major data sources include 12 videotaped whole-class discussions focused on group presentation of arguments to obtain peers' critiques across two course units, the ecosystem and the human body systems, over a 16-week period. Grounded in a qualitative, interpretative approach, the results show that when students' epistemic uncertainty was leveraged as a resource, students were able to construct a more coherent and consistent knowledge system by integrating their prior and target scientific knowledge. We argue that to effectively use students' epistemic uncertainty as a pedagogical resource in managing uncertainty, teachers need to consider the status of students' knowledge of the target concept, if they are aware of uncertainty, and how uncertainty is resolved through critique that leads to knowledge construction. As students had opportunities to practice managing uncertainty, they developed skills necessary to attend to each other's utterances and use them as collaborative epistemic resources to develop, with their peers, acceptable knowledge. Conceptualising argumentation as an enterprise to manage uncertainty can help instructors to design a productive and authentic environment to facilitate the learning of science.