The literature on aid allocation shows that many factors influence donors’ decision to provide aid. However, our knowledge about foreign aid allocation is based on traditional foreign aid, from developed to developing countries, and many assumptions of these theories do not hold when applied to southern donors. This article argues that south-south development cooperation (SSDC) can be explained by the strength of development cooperation’s domestic allies and foes. Specifically, it identifies civil society organizations as allies of SSDC and nationalist groups as opponents of SSDC. By using for the first time data on SSDC activities in Latin America, this article shows the predictive strength of a liberal domestic politics approach in comparison to the predictive power of alternative explanations. The results speak to scholars of both traditional foreign aid and south-south development cooperation in highlighting the limits of traditional theories of foreign aid motivations.