This chapter traces the evolution of the environmental dimension – operationalised as programmatic change, policy integration and environmental actor participation – in European Union (EU) Cohesion policy over time. While in the early years Cohesion policy was closely tied to an economic growth agenda without explicit consideration of environmental policy, the green dimension emerged in the late 1980s in order to support (costly) compliance with EU environmental policy in economically lagging regions and states. After a temporary dropping of the agenda in the early 2000s, the environmental dimension was revived in the context of the post-Lisbon strategy. The authors argue that the economic framing of environmental spending, as implied in the term ‘green economy’, and the special emphasis on climate change, created a window of opportunity for some policy and procedural reforms in the direction of environmental or climate policy integration in the latest generation of Cohesion policy. These reforms now have to stand the test of implementation.