Bioprospecting agreements and Payments for Environmental Services (PES) are both based on the promise of market environmental efficiency. By adapting the concept of the “economy of promises” (developed by Science, Technology and Society scholars, regarding technological innovation) and applying it to institutional and political innovation, this paper analyses the rhetorical dimensions, the performativity, and the implementation of bioprospecting agreements and PES. We argue that the strength of these mechanisms lies in their performativity — in particular, in their ability to shape institutions in a neo-liberal fashion, rather than in their actualisation as markets or their environmental achievements, which are both incomplete and difficult to accomplish. Far from realising the free-market ideal that they are purported to achieve, these mechanisms actually perform incomplete commodification, they require complex institutional arrangements in order to be effective, and they give rise to a low volume of transactions. The economy of promises provides a fresh and complementary reading of the neo-liberalisation of nature as a complex of discursive, institutional and material dimensions.