In this article, we will analyse the relations between Spain and Chile during the transition to democracy in Spain (1975-1982). The focus is on Spanish civil society (political parties, trade unions, civic associations, etc.) and on the mechanisms of solidarity supporting the political opposition, the detained-disappeared and their families, and Chilean society in general. By studying the typology of these mechanisms and their evolution, we will argue that civil society can influence and even reorient diplomatic relations between countries.