The affordances of social media have enabled organisations and members to negotiate and co-create their identities. Despite the original conception of acculturation as a reciprocal process of cultural change, how an organisation adapts to the cultures of its members and how members react to these efforts remain under-researched. Drawing on theories of identity construction, this paper conceptualises two-way acculturation in social media and investigates the role of institutional efforts in building member relationships. We employed a mixed method consisting of a netnographic analysis of university Facebook pages and a quantitative survey with a sample of 410 students to examine how brand page identification and the institutional image (i.e., distinctiveness, prestige, and supportiveness) mediate the relationship between the social media marketing efforts and member-institution identification. The results show that, overall, content tactics (i.e., symbolic resource integration, hedonic quality, and utilitarian quality) and marketer traits (i.e., effort to foster member embeddedness and warmth) not only strengthen member engagement but also help shape an attractive identity of the institution that builds relationships. This paper advances our understanding of identity co-creation and acculturation in social media while also contributing a nuanced understanding of the effectiveness of various engagement tactics to theory and practice.