This article is concerned with the development of a conceptual framework of the key antecedents that lead to sustainable environmental behavior amongst employees within a large organizational setting. A range of quantitative and qualitative methods was employed in the study to examine behavior. Using the Cornwall National Health Service (NHS) in the United Kingdom as a case study, the research demonstrated that both organizational and individual/cognitive factors served as key predictors for sustainable waste behavior. However, these factors did not work in isolation but rather, within a dynamic, holistic, intrarelated, and interrelated conceptual framework to ultimately determine individual behavior. The results suggest the need to address both categories of variables when developing policies to achieve greater sustainability in the behavior of employees within large organizations.