Since its launch in 2021, the Climate and Environment Charter for Humanitarian Organizations (the Charter) has been signed by hundreds of humanitarian actors across the world, including local and national organizations, United Nations agencies, National Red Cross and Red Crescent Societies, and large international NGOs. The Charter's development grew out of a sector-wide recognition that humanitarians have a role to play in addressing the crises of climate change and environmental degradation, and that fulfilling this role would entail changing how they work. Two years into its existence, the Charter has helped build momentum towards this change and has provided a useful measurement tool for how much remains to be done. This paper traces the origins, inspiration and process of the Charter from the perspective of the present authors, who co-led the Charter's development. The article highlights some of the challenges that we faced and how these were addressed. In taking stock of progress towards the Charter's goals, the article flags areas where further effort is needed to adequately strengthen the humanitarian response to the climate and environmental crises.