This article interrogates United Nations (UN) calls that ‘making peace with nature’ should become the crucial mission of the 21st century. It ponders the kind of diplomacy envisioned for such a reconciliation ecology to be credible. Drawing on one of the most promising and less known programmes of the UN system – namely, Harmony with Nature (HwN), which pioneers Earth-based jurisprudence and rights of nature – it conceptualises this diplomatic shift and assesses the conditions under which ecological diplomacy can be productively operationalised in the 21st century vis-à-vis a mere rhetorical appropriation and co-optation by intergovernmental agendas. Building on Indigenous thought and animist epistemologies, programmes such as HwN espouse a new relationship with Planet Earth and make it possible to explore ‘nature’ as diplomatic interlocutor. We argue that existing paradigms of peacebuilding fail to sufficiently capture the diplomatic aspects and complex local dynamics of the human–nature relationship and suggest a reconceptualisation based on an ecological diplomacy that is both expansive and transformative and views this relationship as one of troubled coexistence.