The third ESSA Summer School in Social Simulation was held in Toulouse, France on 2-6 July 2012. The programme consisted of two lectures per day from experienced modellers, and a tutorial session led by experienced researchers where participants acquires practice on agent-based simulation platform and social network analysis tools. The Faculty included Olivier Barreteau (IRSTEA, France), Guillaume Deffuant (IRSTEA, France), Bruce Edmonds (Manchester Metropolitan University, UK), Nigel Gilbert (University of Surrey, UK), Klaus Troitzsch (University of Koblenz-Landau, Germany) and Armando Geller (GroupW, USA), among others. The school was sponsored by European Social Simulation Association, Institut de Recherche en Informatique de Toulouse and Université Toulouse 1 Capitole.