Since its emergence in the mid-1990s, unauthorized small-scale gold mining—widely known as “ninja mining”—has grown to become a central element of Mongolia’s informal economy, engaging tens of thousands of people in seasonal, unregulated, and occasionally dangerous labor. In this paper we set out to show that the story of ninja mining is illustrative of the wider transformation of political economy that Mongolia has experienced, in which a de facto public resource was created in the wake of the collapsed state socialist economy, only to be progressively privatized and enclosed by increasingly powerful mining company interests. We examine the implementation of a development project aimed at providing sustainable livelihoods for those engaged in unauthorized mining. Drawing upon anthropological critiques of development, we explore the ways in which the project, while arguably succeeding in its own terms, failed to meet the expectations of the miners involved. Committed as it was to working within the new private property regime for land introduced by “neoliberal” reforms, the project constructed the ninja “problem” in terms of a lack of formalization and training. It was ultimately unable to address the fundamental issues of property relations and access to resources that lie at the heart of the ninja phenomenon.