Although transparency on the sustainability of public services is an issue of urgent interest to both governments and academics, previous research in this area has mainly focused on developed European countries, and has paid insufficient attention to areas that are still developing, such as many Latin American countries. The aim of this study is to identify factors that promote transparency on sustainability by local governments in Latin America, in the view that greater transparency will help them meet the goals of the 2030 Agenda for Sustainable Development. Therefore, using content analysis and following the GRI guidelines, we analyze the economic, social and environmental information published on the websites of 200 large local governments in 18 Latin American countries. In addition, using linear regression and calculating the corresponding Spearman coefficients, we analyze the influence of idiosyncratic and systemic variables on the volume of information disclosed. Our findings show that certain factors—population size, education level, unemployment, the quality of legislation and political corruption—affect transparency on sustainability. The conclusions drawn from this analysis enable us to identify useful measures for enhancing transparency on sustainability, including the reform of transparency laws and the analysis and disclosure of citizens’ information demands.