There is an extensive literature on environmental governance, which refers to multi-stakeholder processes to arrive at collective decisions about how natural resources will be managed. Recent work on environmental governance has focused on outcomes in terms of social-environmental sustainability. However, questions remain about the effectiveness of environmental governance in practice for yielding sustainable social or environmental outcomes. In cases where environmental governance processes prove ineffective, political ecology offers analytical approaches involving explanations that can account for unsustainable outcomes. In addition, an emergent literature on environmental governance provides frameworks to evaluate its effectiveness by unpacking it with regard to diverse criteria. These two literatures together permit analysis of how political ecology and other potential explanations can account for ineffective environmental governance in terms of specific unmet criteria. Analysis of ineffective environmental governance is likely to be especially valuable in a comparative perspective, in which multi-case studies can reveal the extent to which political ecology explanations predominate across cases. We focus on the Amazon, a large region with high social and biological diversity and where competing stakeholders engage in conflict over governance of natural resources. We pursue a comparative analysis of five cases where environmental governance has been ineffective in terms of sustainable outcomes. In each case, we identified five key explanations for ineffective environmental governance. We then coded those explanations with regard to whether they invoke issues highlighted by political ecology. We also coded them considering environmental governance evaluation frameworks to identify the unmet criteria for environmental governance to be effective. We then pursued a comparative analysis of similarities and differences across the cases. The findings indicate that political ecology issues are predominant among explanations for ineffective environmental governance across all five cases. The results also reveal which environmental governance evaluation criteria are most often unmet among the cases. The findings highlight the importance of political ecology for understanding ineffective environmental governance, and permit delineation of specific criteria for effective environmental governance that can be the focus of strategies to improve environmental governance for sustainability.