Small to medium enterprises or SMEs significantly contribute to national economic development and growth. They also have a substantial environmental footprint and effective uptake of sustainability practices is seen as problematic, primarily because of limited resources. This study aims to develop an understanding of awareness and associated sustainability practices by SME owners and extend this understanding towards activating the collective potential of small businesses as environmental agents that research suggests could be powerful. The study used a mixed-method approach based on a survey, interviews with five (5) business owners and secondary data from thirty (30) business reports to explore two research questions (RQ). RQ1, concerned with attitudes and intentions by business owners to implement sustainability practices, was examined using the Theory of Planned Behaviour. RQ2, an exploratory effort to unpack the decision rules that business owners typically adopt in practice, was a qualitative study using interdependence theory. A total of 589 survey responses were received, with 516 surveys retained after data cleansing. The quantitative (deductive) analysis identifies strong awareness of and support for sustainability by business owners: over 90 per cent support (52.34% fully agree and 37.68% concur) the need to adopt and/or integrate sustainability into business strategies. Key drivers noted include owner awareness and knowledge, and sustainability culture has an influence on subjective norms. Barriers to uptake included access to infrastructure and resources, as well as the owner’s mindset. Overall, the evidence is that uptake of sustainability is low, with the data noting general reluctance by nearly 70 per cent of owners to adopt sustainability. For RQ2, analysis based on the Gioia methodology departs from inductive reasoning towards an abductive approach that combines emerging data with existing theory. Practically, at a micro level, this study identifies (internal) structural and (external) environmental interdependencies that shape the trajectory of sustainability uptake. Collectively, distinctive decision rules associated with four entrepreneurial categories are noted: ‘Yes Innovative and ‘Yes Substitute’ that respectively reflect creative or opportunity discovery behaviours, and an allocative (Yes But) cautious approach oriented to immediate returns, but with latent potential for adaptations in relation to sustainability. A fourth significantly large SME category titled ‘No Because’ is also noted. The focus of this category is on survival and maintenance of the status quo. Primary concerns are costs, lack of clarity with sustainability reporting and uncertainty with green tech performance. Theoretically, the study adds two ideas to the scholarly discourse on sustainability practices in Irish SMEs. First, noting two distinct types of business models, value-creation and revenue, this study explains why some SMEs adopt sustainability practices, while others do not. Revenue-based business models lack actor-specific enablers, such as entrepreneurial outlook and strategy planning, and likely only adopt sustainability practices if required. Second, this study draws attention to the less studied processual dimension in theorisation related to entrepreneurial ecosystems. This study presents a process-based framework to navigate the nuanced complexities of the various sectors and local contexts for SMEs. Regulatory clarity aside, wider (collective) uptake is arguably embodied in sympathetic strategy and business model design by SMEs and the creation of ecosystem-wide social capital. Finally, noting the role of external social pressure in shaping sustainability intentions, impact measures that reflect societal expectations, industry norms and networks are highlighted as antecedents to sustainability uptake and to scalable impact.