The aim of this paper is to analyse the organizational model of one of the most successful European radical left parties, the Greek Coalition of the Radical Left (SYRIZA). Our goal is to analyse SYRIZA’s organizational transition from the electoral arena to the government (2015). Our main finding is that SYRIZA started as a socially-oriented organization led by an oligarchic dominant coalition and converted itself into a political party, characterized by a prevailing role of the party in public office/party government. Both the institutional environment and the party organization’s first configuration have had an impact on this change.