Since its publication in 2010, ISO 26000 has become the de-facto standard of Corporate Social Responsibility (CSR). While not a certifiable standard in ISO terms, but rather a guidance document, it has become the document many corporations use as their basis for CSR work. ISO 26000 claims that the objective of social responsibility is to contribute to sustainable development, using the Brundtland definition – development, which meets the needs the present without compromising the ability of future generations to meet their own needs – as the basis for sustainable development. However, the Brundtland definition, while commonly referred to, is not sufficiently concrete to give guidance for strategic planning and action in businesses, municipalities and society at large. Therefore it is helpful to supplement the Brundtland definition with a framework that allows for this concrete and strategic planning, e.g. the Framework for Strategic Sustainable Development (FSSD). The FSSD is based on a principled definition of sustainability, defining social and ecological sustainability in more operational terms, and includes guidelines for how to contribute systematically and strategically to fulfillment of this definition. It is a transdisciplinary framework built on insights from systems thinking and has been continuously developed as well as used and improved in organizations all over the world for the last two decades. A particular recent development focus has been the social dimension of sustainability, with new insights based on the application of systems thinking to social systems having been recently presented. In this paper, these new insights are used to analyze and evaluate ISO 26000´s contribution to sustainability, highlighting both benefits and shortcomings of ISO 26000 from a social systems and strategic sustainable development perspective. Main points include that, while ISO 26000 is comprehensive in it´s scope and provides a vast achievement in terms of international consensus building around the essential issues in CSR, it is not based on a scientific understanding of social and ecological systems and is therefore a document highlighting current societal expectations rather than a document allowing organizations to innovate, plan, act and monitor long-term for sustainability. The paper further points out examples of aspects of sustainability that are likely to become issues in the future, but that are currently not covered by the ISO guidance. Finally, the paper points at research needed to explore more in detail in which ways ISO 26000 can support strategic working towards sustainability, and in which areas other tools are necessary.