While 148 of the 196 national constitutions in effect today manifest some form of environmental constitutionalism, the fact that some states have not adopted such provisions suggests that their spread is not inexorable. This article investigates the factors which affect whether a state adopts environmental constitutionalism. By undertaking a historical analysis of those countries which have so amended their constitutions, it identifies the context in which the constitutional change takes place as a significant consideration. The context of constitutional change influences the amendment process, which is then opened up to a range of other factors, both external (learning/persuasion, acculturation/emulation) and internal (political leadership, public and sectoral engagement, constitutional ideology, national environmental damage), all of which are considered by examining previous efforts to enshrine environmental constitutionalism. The article concludes by highlighting four specific responses that are key to successful amendment processes, namely: capitalizing on crisis situations; ensuring that economic concerns are adequately addressed; leveraging the support of the public and politicians; and linking environmental protection to national values.