Social media is being used by a large part of local administrations. As a highly disruptive adopted innovation, it is important to understand the process of institutionalization through empirical variables. This paper studies the Dutch case to analyze to what extent social media technologies have being institutionalized within major city councils in Netherlands. The study tries to answer the following research question: What is the level of institutionalization of social media in Dutch city councils with more than 50,000 inhabitants? Taking this into account, this work is based on two analytical levels: on the one hand, it performs a comparative analysis of Dutch city councils that responded to a survey on social media institutionalization. On the other hand, based on previous descriptive empirical results, the paper studies Utrecht as a case of success to analyze the level of social media institutionalization through Social Network Analysis and automated natural language processing with data crawled from Twitter. Overall, results show that social media institutionalization in Dutch city councils has been high, developing decentralized practices with formal commitments for social media use and with a high sense of leadership, showing interesting participatory and public service delivery logics. At the same time, the case of Utrecht confirms that a high level of institutionalization requires management capabilities and goals definition and implementation, including a conversational approach to citizens, and an emerging approach to public service delivery.