Current human activity is unsustainable in terms of planetary boundaries and citizens and governments in industrialised nations, such as Australia, may need to assume greater responsibility and shift towards more sustainable behaviours and lifestyles. There has been a plethora of research aimed at developing policies which foster more sustainable behaviours and consumption. However, the effectiveness of promoting specific behaviours has been questioned by some authors who argue that encouraging more comprehensive changes in people’s behaviour and time use in the form of sustainable lifestyles may provide a more effective approach to achieving ‘sustainability’ (Backhaus, Breukers, Mont, Paukovic, & Mourik, 2013; Defra, 2011; Shirani, Butler, Henwood, Parkhill, & Pidgeon, 2015; Task Force on Sustainable Lifestyles, 2010). Under the assumption that lifestyle changes may be critical in effecting such a transformation, the aim of this research was to identify the key psychological and behavioural factors that characterise and influence different lifestyle choices in Australian societies. The primary research methodology has been based on an on-line survey. Key explanatory variables adopted were drawn from the Theory of Planned Behaviour, Norm Activation Model, New Ecological Paradigm scale and from the broader literature on sustainable living. The main dependent variable of focus was self-identified commitment to sustainable living (measured on a 4-point Likert scale). The sample consisted of 1,002 participants that were broadly representative of the adult Australian demographic in age, gender and living location. The main findings of this work relate to people’s beliefs about sustainable living, social identities, social norms, and feelings of moral obligation to live more sustainably. Firstly, the notion of a ‘sustainable lifestyle’ is not tied to a fixed definition and can be interpreted somewhat differently by different segments in society. This represents an opportunity for policy makers to reposition inhibiting beliefs such as ‘sustainable living is too expensive or difficult’ towards more ‘attractive’ beliefs about this lifestyle. Further, sustainable lifestyles have potentially strong ties to social identities. Hence, sustainable living may need to be positioned in a manner that minimises inter-group conflicts in social identity formation. Minimising inter-group conflicts can be approached by influencing social norms related to sustainable living (for instance, by ‘normalising’ this lifestyle into a mainstream concept using social marketing techniques). Given the empirical findings of this research, we provide some policy suggestions on how to influence social norms and identities so that sustainable lifestyles might become more appealing to a wider range of individuals in society. Feelings of moral obligation to live more sustainably were not shown to be correlated with the survey respondents’ awareness of worsening environmental conditions. Hence, motivational policies – that are guided by a ‘positive psychology’ perspective – may represent worthwhile avenues to influencing individuals to feel more responsible and morally obliged to (want to) adopt sustainable lifestyles. These ‘motivational policies’ may also be actioned via people’s social identities and social norms. For instance, people are more likely to be influenced by others in their ‘ingroup’ (e.g. their shared social identity group, such as political orientation). Hence, messages aimed at encouraging more sustainable living, which originate from other ingroup members (for instance, members of the same political identity) have the potential to be more well-received by certain segments in society. Lastly, ‘sustainability’ is a broad concept that can be interpreted in different ways. As such, to indicate somewhat more narrowly what this study was referring to in discussions of ‘sustainability’ and ‘sustainable lifestyles’, the degrowth scenario was used as the overarching theoretical platform. Degrowth emphasises the importance of reducing material consumption (one of the behaviours investigated in this research) and argues that ‘technology fixes’ may be insufficient to achieving a sustainable scenario. Degrowth also advocates for a temporary and controlled economic contraction as a precursory step to a ‘steady state’ economy. Lastly, the literature on degrowth was used in this study to help validate the argument that encouraging a wide-spread adoption of sustainable living in Australia (through policy interventions) is a likely ‘necessity’ for sustainability.