Small hydropower is poised to undergo a global boom, potentially accounting for as much as 75% of new hydroelectric installations over the next two decades. There are extensive bodies of literature arguing both that small hydropower is an environmentally benign technology benefitting rural communities, and, conversely, that unchecked small hydro development is a potential environmental calamity with dire consequences for rivers and those who depend upon them. Despite this debate, few studies have considered the ways in which small hydropower is socially constructed in the sites targeted for its development. This paper focuses on the Bobos-Nautla River Basin, in the Sierra Madre Oriental of Mexico, where numerous small hydropower projects are planned. The central argument is that the dominant framing of small hydropower in Mexico focuses on claimed benefits of 'clean' energy, sidelining any consideration of impacts on water resources and local environments. However, even if this narrative has dominated policy-making, it is being actively contested by a social movement that constructs these projects as water theft. The narratives surrounding small hydropower are reconstructed from interviews with government officials, activists, NGO workers and residents of communities near project sites conducted during ten weeks of fieldwork in 2014. The results of this fieldwork are contextualised by an overview of evolving trends in hydropower governance globally that situates the boom in small hydro within shifting relationships between states, international financial institutions, and private finance, as well as an historical account of the evolution of hydropower governance in Mexico that speaks to long-standing conflicts over water use for hydroelectric generation.