The term ‘sustainable consumer’ (SC) is used across various knowledge domains, from sustainable consumption, green marketing, sustainability, and social change to social marketing for sustainability issues. However, the term SC lacks a precise definition, which leads to the inaccurate evaluation and measurement of the impact of green marketing or social marketing campaigns on consumption—sustainable or otherwise. This paper develops a framework to clarify the term ‘sustainable consumer’ to assist both scholars and practitioners. The application of systems thinking was applied to the extant literature to theorise the SC. This conceptual paper provides a new framework for theorising SCs: the integrated model of the sustainable consumer (ISMC). This framework emphasises the interconnected relationships of influences within the SC profile to assist scholars in examining SCs within these systems with precision. We contend that, to promote and maintain the desired sustainable consumption for long-term effects, researchers and practitioners should consider the impact not only of the socio-psycho-demographic characteristics but also the connection of the person to the environment and their community, in addition to their worldviews. The framework presented here challenges linear models by proposing a nested, dynamic structure that recognizes the interconnected influences within the sustainable consumer’s ecosystem. The framework also enables a targeted intervention design according to the layer and element and permits more precise evaluations of behaviour change campaigns’ effectiveness.