Sustainable healthy diets meet nutrient requirements and are environmentally sustainable, and socioeconomically and culturally appropriate(1). The UK Livewell Diet was developed using optimisation modelling to meet national nutritional recommendations, be socially acceptable and minimise environmental impacts related to carbon footprint, land and water use, acidification, eutrophication and biodiversity loss(2). Versions of the Livewell diet have been developed for other countries, but not currently Australia(3). This study aimed to adapt the UK Livewell diet(2) for the Australian context and assess the potential dietary and nutritional implications of adoption by Australian adults. To adapt the UK Livewell diet to Australia, we calculated recommended percentage changes in intake across 29 food groups between the average UK diet (ages 19-64 years) and the Livewell diet. These changes were then applied to the average dietary intake for Australian adults (19-70 years, n = 14,944) from the Australian 2011-2 National Nutrition and Physical Activity Survey(4). Due to the modelled 18% reduction in total energy intake, compensatory adjustments were made by increasing cereals (+59g), potatoes (+71g) and fat/oils (+16g). This resulted in the Adjusted Australian Livewell Diet (AALD) – estimated energy content 8,456kJ (5% lower than 2011-2 adult mean). We compared the AALD with the 2013 Australian Dietary Guidelines recommendations(5) and modelled its likely impact on key nutrient intakes using substitution dietary modelling. Compared with 2011/12 Australian diets, the AALD was substantially lower in animal-source foods – red and processed meat, shellfish and cheese were decreased by 67%, poultry by 61%, eggs by 33% and milk/milk products by 13%. Intakes of other foods were also reduced: milk alternatives (-59%), snacks/desserts (-53%), sugar/confectionery (-47%), and fruit juice and miscellaneous foods (-46%). In contrast, intake of fish increased by 102%, meat alternatives by 114%, cereals/cereal products by 68%, fruit by 48%, potatoes by 59% and other vegetables by 44%. To adopt the AALD, Australian adults would need to increase their daily intake by an average of 0.4 serves of fruit, 1.6 serves of vegetables and 2.2 serves of grains, and reduce their intake of both the meat/alternatives and the dairy/alternatives food groups by 0.3 serves. Replacement of the Australian diet with the AADL would likely increase intakes of dietary fibre (+26%), long chain omega-3 fatty acids (+31%), vitamin A (+14%) and folate (+23%), while reducing intakes of sodium (-15%) and saturated fat (- 11%) – changes considered beneficial. However, protein (-18%), riboflavin (-15%), vitamin B12 (-27%), calcium (-11%), phosphorus (-12%) and zinc (-18%) intakes would likely decrease, potentially exacerbating existing inadequacies in Australian adults. Adoption of the AALD may both positively and negatively impact adult nutrient intakes. Further research evaluating potential effects on usual dietary intakes of all population groups and achievement of nutritional recommendations is recommended.