The implications of the planetary boundaries (PBs) proposal involves scien- tific, moral and political dimensions. The core of the PBs idea is that humankind is transgressing global environmental tipping points resulting in changed conditions that threaten to unravel human progress. The growing status of the proposal potentially makes it a highly influential organising concept that seems to contain within it aspirations to dra- matically reconstitute the relationship between society and the environment—thereby transforming the politics of sustainable development. This paper situates PBs in contem- porary green thinking. Key planning events and related documents supporting the Post- 2015 Development Agenda process are then examined to identify strategies and reactions to the PB proposal. The findings show that divisions reminiscent of older North/South environment and development tensions related to the role of experts, democracy and the Right to Development threaten to prevent PBs from being mainstreamed in key UN environment and development programmes and fora.