Since the release of the Brundtland Report in 1987, the concepts of sustainable development and sustainability have gained momentum, particularly with the onset of current social and environmental issues, including climate change. That said, more than 30 years later, there remains no consensus as to what constitutes sustainability. In particular, in tourism various discourses surrounding these concepts have emerged. Many scholars and practitioners see sustainable tourism as a means to address unsustainable activities in the industry. However, due to the vagueness of the concept, sustainability is difficult to navigate, and has led to confusion amongst social and political actors in this area. This has resulted in a plethora of articulations (for example ecotourism and Indigenous tourism), measurements (for example indicators and standards) and expertise. Given the multitude and complexity within the overarching discourse of green politics, this thesis sets out to explore how one particular discourse, namely eco-certification, was created and shaped over time. I use Discourse Theory and the Logics of Critical Explanation to examine the eco-certification process of Ecotourism Australia, a national certifying body in the Australasian region, to illustrate how accreditation and certifying bodies created sedimented practices (‘rules of the game’) and disseminated them amongst through the industry. The study finds that the concepts of sustainability and eco-certification have been redescribed to facilitate the subsumption of sustainability into the dominant economic system. Rather than seeing ecotourism as a new paradigm within sustainable tourism, certification bodies regard it as a new market opportunity to which eco-certification provides the necessary access. Eco-certification is a business development tool, adding value to businesses and more importantly permitting them to continue with business-as-usual practices. Thus, eco-certification and sustainability have been subsumed by the business case and legitimised by the tourism industry that shows little interest in recognising alternative pathways to social and environmental sustainability.