The aim of this article is to analyse the evolution of the Movimento Cinque Stelle (Five-star Movement, M5s) in the city of Turin from its beginnings to the election of Chiara Appendino as mayor in June 2016 in order to assess the impact of the passing of the threshold of government on three distinct areas: party organisation, the party’s identity and ‘ideology’ and the Movement’s relationship with citizens, social movements and the local media. Although an organisation similar to that of traditional parties has not developed over time, the results show that with the passing of the threshold of government the M5s became more centralised, and personalisation processes emerged: in the absence of a formalised party structure, the candidates and then the elected representatives gained significant decision-making powers. Moreover, administrative constraints led the M5s to scale-down its programme, to pursue policies it had previously challenged and to normalise its relationships with political opponents. Born openly contesting traditional party structures and pledging a radical change to the system of power that had ruled the city for the previous twenty years, nowadays the M5s in Turin oscillates between two poles, halfway between its original identity and institutionalisation. On the one hand, there are the social movements that supported the M5s and from which the first activists were drawn; on the other, government responsibilities and the expectations of those who do not belong to the milieux from which the M5s originated but who voted for Appendino in 2016.