Social media institutionalization in public administrations has been conceptualized as the final stage of the adoption process. However, an understanding of organizational models for social media institutionalization in public administration is lacking. This exploratory study of Dutch local governments contributes to the literature by identifying how governments organize social media institutionalization. Drawing on an original questionnaire on social media adoption, two advanced cases were selected based on their high level of social media institutionalization: Utrecht and Eindhoven. For each case, in-depth semi structured interviews were carried out aiming at detecting institutionalization patterns. Our study highlights that, in contrast with the literature on stages of technological maturity, social media institutionalization shows two different organizational models: a centralized model, based on trust, with highly structured and formalized policy guides, low experimentation, formal training and evaluation supported by standardized reports; and a distributed model, based on control, with simple guiding principles, higher levels of experimentation, training build on a “learn by doing” basis, and individual evaluation mechanisms. These results enrich current academic understanding of social media institutionalization and may guide public officials involved in social media institutionalization practices.