The global environmental crisis has prompted the development of a wide range of tools to define firms’ relation with nature, such as environmental management systems standards. Few studies have so far explored the puzzle raised by the development of natural capital accounting methodologies. Such instruments aim at assigning a book value to nature, which allows an environmental costs and benefits analysis. The International Organization for Standardization (ISO) is currently setting standards for such methodologies (ISO 14007 & ISO 14008). Other actors, including the Big Four accounting and auditing firms – Deloitte, E&Y, KPMG and PwC –, and the Natural Capital Coalition, already developed their own methodologies outside the scope of ISO. This paper examines why and how ISO develops natural capital accounting standards that are likely to compete with other arenas. We build from semi-structured interviews with key stakeholders of ISO. We suggest that the development of ISO 14007 & ISO 14008 compete with the existing methodologies of the first-movers, in particular on concerns regarding transparent documentation and reporting. We build our argument on international political economy approaches to emphasise the link between technical specifications and power relations in contemporary capitalism.