Stormwater harvesting and treatment will be critical systems within water-sensitive cities. Although water practitioners acknowledge the importance of developing stormwater as a water source, their risk perceptions might be barriers. Risk perceptions can be understood within a receptivity framework, with awareness, association, acquisition and application components. In this study, water practitioners' risk perceptions of stormwater harvesting and treatment in Australian cities were examined within this framework, to identify where to focus reform efforts within the water industry to improve their adoption. Analysis of data from an online survey exploring water practitioners' (N = 620) perceptions of risk of alternative water systems revealed that three-quarters of respondents thought stormwater harvesting and treatment yielded at least moderate benefits, supporting fit-for-purpose use of treated stormwater and installation of the infrastructure in different contexts. Perceived general risk of each was slight, although stormwater harvesting was perceived as more risky than treatment, and this difference persisted for specific risks, e.g. public health, environmental. In terms of the receptivity framework, perceived specific risks of stormwater harvesting and treatment systems challenge, to different extents, the practitioners' association, acquisition and application of the systems in Australian cities. In particular, reform efforts should be targeted to perceived management and cost-related risks.