In Senegal, the government has encouraged private investment in agriculture and biofuel production since the 2000s, generating several attempted or effective large-scale land acquisitions by domestic and international investors. In reaction to these projects, local groups of opponents have joined forces with national peasant organizations, civil society associations, and think tanks to resist perceived land grabs. This article examines the emergence of this social movement and explains why anti-land grabs campaigns were successful in halting some projects, but not successful in others. I argue that four main factors are at play: a strong mobilization of local populations measured by group cohesion and level of determination; the assistance of national and international NGOs in scaling up protests beyond the local level; the capacity of opponents to harness the support of influential elites and decision-makers; and the legal status of the land under contention. This paper draws on an analysis of secondary data, qualitative interviews, and field observations carried out in Senegal for several months from 2013 to 2018.