Modern organisations increasingly experience pressure from regulatory, normative, and social sources to be more environmentally friendly. Extant research shows that employee engagement in proenvironmental "green" behaviours enhances organisational outcomes regarding environmental sustainability. Despite contextual differences between the workplace and the home, however, and evidence that people differ in their green behaviour across these settings, contemporary explanations as to why employees engage in green behaviours at work continue to draw from environmental psychology research on private green behaviour at home. Thus, there is a need to understand more clearly the nature of green behaviour as it occurs specifically in the work context. This requires an approach that considers the organisational context as a contributing factor, and acknowledges that green behaviour at work constitutes a particular form of job performance. In this research therefore, I sought to address these points by investigating how employee perceptions of the organisational context influence both required (i.e., task-related) and voluntary (i.e., proactive) employee green behaviour (EGB). Consistent with this aim, I collected data from employee samples uisng constructs from organisational behaviour, such as organisational climate and job performance, in a multilevel and mixed-methods program of research.In Chapter 1 (Case Study), I briefly outline the climatic changes that are prompting organisations to engage with environmental sustainability. I outline macro-level organisational activities and present a case study that highlights the central role of employee behaviour. Finally, Icritique the literature and identify three limitations that inform the research questions I address through my program of research.In Chapter 2 (Systematic Review), I present a detailed review of the EGB literature, and organise research findings into a multilevel conceptual framework. Within this framework, Ipropose that person and context factors contribute to motivational states that drive required (i.e., task-related) and voluntary (i.e., proactive) EGB. Based in this literature, I outline an agenda for future research to answer key questions to move the literature forward.In Chapter 3 (Study 1), I describe a study of how perceived organisational policy for sustainability effects EGB, and whether or not perceptions of green climate mediate this relationship. I used a cross-sectional survey design to collect data from a sample of office workers (n = 168), and developed a green psychological climate construct comprising perceptions of the organisation and co-workers. Using structural equation modelling, I found unique effects for different perceptions on types of employee green behaviour. Specifically, climate perceptions regarding the organisation mediated the effect of perceived sustainability policy on task-related EGB; whereas climate perceptions regarding co-workers mediated the effect of perceived policy on iii proactive EGB. This study highli...