Case studies are a useful means of capturing and sharing experiential knowledge by allowing researchers to explore the social, organisational and political contexts of a specific case. Although accounts of action learning are often reported using a case study approach, it is not common to see individual case studies being used as a learning practice "within" action learning sets. Drawing on a network action learning (NAL) project, this paper explores how the process of coaching, articulating, authoring, sharing and editing case studies provided a vehicle for learning and research within a NAL set. The intended contribution of this paper to the theory of action learning is to extend the range of learning practices to include the case study within the NAL set. It discusses how case studies act as boundary objects, which are artefacts that can be used to cross boundaries between groups in order to facilitate learning that might not otherwise occur.