Following the publication of the 2011 United Nations Environment Programme (UNEP) Green Economy Report, the UNWTO published the Tourism in the Green Economy report as clear evidence of the tourism sector’s growing influence on green economy. This paper provides the first narrative review on green tourism economy based on all available published research. The paper synthesizes existing knowledge, reviews responses and initiatives on green tourism, and suggests future research and methodological approaches to help advance this field. The Scopus and WoS databases were used for the bibliometric study. The results are structured into three sections—challenges, opportunities, and enabling conditions—which comprehensively cover the main themes. Tourism in the green economy refers to tourism activities that can be maintained, or sustained, indefinitely in their social, economic, cultural, and environmental contexts: sustainable tourism. Sustainable tourism is not a particular form of tourism; rather, all forms of tourism can strive to address this approach, considering the needs of visitors, industry, the environment, and host communities. There is growing recognition of the tourism sector’s potential contribution to the green economy through more sustainable practices, climate change mitigation and ecotourism. Greening tourism involves policies and programmes that consider not only tourists’ expectations for the responsible management of natural resources but also the needs of the communities that tourism schemes support or affect. Therefore, sustainable tourism aims to increase efficiency in the use and conservation of energy, to minimize waste and to increase awareness and support for the sustainable use of natural resources such as water, to conserve biodiversity, cultural heritage, and traditional values, and to generate local income and strengthen local communities with a view to improving livelihoods and reducing poverty. The contribution and influence of the tourism industry on the green economy is gaining attention from academics, practitioners, and policymakers. In this sense, research and the scientific literature have produced a substantial and growing body of knowledge about tourism in the green economy that highlights the challenges and opportunities that open up to the green economy and its specific applications. In this context, this paper examines and evaluates the existing literature on tourism in the green economy. Through a systematic literature review, 327 articles from the Web of Sciences (WoS) and Scopus databases are analysed and synthesized into an integrative framework that links the green economy of tourism with its background and consequences. The bibliometric analysis and the narrative review that is carried out on the articles in the sample offers a twofold contribution. First, it provides scholars and practitioners with a synthesis of the state of the art of the issue, in which the main lines of knowledge and the development towards greener tourism are indicated. Second, it helps to identify gaps and research directions that academics need to address to further develop the existing body of knowledge on tourism in the green economy.