The world needs more urgent and ambitious action to address climate change. Seventy-one countries have pledged to reach net-zero emissions by midcentury. Nevertheless, achieving decarbonization and adapting to climate change will require fundamental changes in the production of goods and services by firms and the consumption patterns and behavior of citizens. Climate change poses difficult challenges for policy makers, and three particular challenges make the open government principles of transparency, participation, and accountability especially important. First, countries often face the political challenge of credibly committing to climate action over the long term, in that they must commit to action over multiple electoral cycles if the private sector, households, communities, and public entities are to adopt new technologies and change behavior. Second, climate change requires coordination between government and nongovernment actors, as there will be winners and losers along the way and governments will need to work toward consensus to balance the outcomes. Third, governments have to translate promises into climate action. The principles of open government can be especially useful in tackling all three challenges by harnessing and ensuring citizen trust in government and in the legitimacy of climate-directed policy decisions. This note will show how the use of open government principles and mechanisms can make a notable contribution to climate change action. It provides examples of such measures as well as an inventory of existing good practices and tools, which can serve as a source of inspiration for policy makers and citizens alike.