Climate-driven changes in species’ distributions can affect ecosystem function, fisheries and conservation, presenting challenges for management. A recent review of the scientific literature1 revealed 198 species shifting in Australian waters along with gaps in our knowledge and highlighted a role for citizen science data to yield insight into these phenomena. Over the past decade, several citizen science programs have collected large amounts of species observations that could be used to help address these gaps, but these databases have not yet been systematically searched and analysed to characterise species redistributions. We used a qualitative decision tree analysis [2] to assess potential extensions of marine species distributions around Australia, with data from three citizen science projects (Redmap; iNaturalist Australasian Fishes project; and Reef Life Survey). This analysis considers historical (i.e., recognised as of 2012) distribution limits, along with species traits (e.g., migratory behaviour, detectability) and evidence provided by citizen scientists’ data (e.g., possible overwintering and/or multi-year observations) to assess confidence in redistributions occurring among a list of 200 species tracked by Redmap over the past decade. Of 197 species represented in the citizen science databases, we identified 77 as having been detected out-of-range by citizen scientists (31 were classified with high confidence, eight with medium confidence, and 43 with low confidence). The mean extent of extensions assessed was 316 km (max. 1474 km). Our findings suggest priority species and regions where targeted scientific research may be appropriate. Further, results of the assessment have been incorporated into report cards — four-page print and web versions for NSW, TAS, and WA, and this A1 poster summarizing the results across the Australian marine estate. The report cards provide communication tools for dissemination to demonstrate the scientific value of citizen science and engage with the broader public on climate change, using their own observations.