In the wake of progressive globalization and accelerating speed of change, corporations are increasingly faced with so-called meta-problems, whose complexity tends to outstrip the sensemaking capacities of individual organizations. As a response to that, organizations are increasingly engaging in inter-organizational sensemaking activities in order to develop a collective understanding of these meta-problems to inform their intra-organizational attempts at dealing with them. In this paper, we propose to conceptualize such inter-organizational strategizing processes as scaffolding of sensemaking capacities. Based on a longitudinal case study of a multi-sector industry initiative concerned with the meta-problem of water as an environmental resource constraint, we explore the different practices and patterns in which individual organizations extend their respective sensemaking capacities. We identify three categories of extension practices (scaffolding practices, conduct practices, transfer practices) and three patterns of extension (extension for triggering sensemaking, complementary extension, selective extension). Overall, we contribute to the literature on strategy-as-practice, the wider sensemaking literature and the literature on inter-organizational strategy.