Post-Keynesian environmental economics provides a realistic view of the impact of different environmental policy instruments in modern capitalist economies and, in turn, guides the design of policy aimed at improving environmental conditions and reducing energy and material throughput. Post-Keynesian environmental economists criticize the orthodox approach to the environment and the framework of those ecological economists relying on neoclassical principles, since these models neglect fundamental uncertainty, endogenous preferences, path dependence, a foundational role for money, the distribution of income, nonergodic processes, complex system dynamics, and economic power relations. This chapter begins with a brief history of post-Keynesian environmental economics before addressing the reasons for the lack of attention devoted to environmental issues in post-Keynesian economics. It also explores justifications for prioritizing environmental sustainability within post-Keynesian theory and discusses some of the ways the environment can be embedded within post-Keynesian theory. The chapter concludes with a critique of orthodox environmental economic policy and a post-Keynesian alternative.