The transformation of local state institutions by way of the paradigm of the common – the creation of commons–state institutions – has become one of the strategies of new municipalist practices. It is an attempt to overcome two crises: the crises of both the privatised and the bureaucratic state forms. It aims to take back the production and distribution of the ‘public’ by the state and to democratise this process. The article analyses the discursive use and material implementation of the paradigm of the common in the transformation of local state institutions, and how contested meanings attributed to it by different actors may influence the definition of commons–state institutions. It analyses two new municipalist contexts, Naples and Barcelona, and examines the common-inspired transformation of their local public services: water services and sociocultural facilities, respectively. It argues that commons–state institutions are negotiated institutional configurations that emerge from the synthesis of the situated and experimental interpretation of the paradigm of the common shared by (different segments of) state and civil society actors, and whose governance needs to be adequately and openly codified to make them robust and enduring.