With the rise of online communities, research has focused on how to manage the communities and foster members’ knowledge-sharing intentions. While prior studies have emphasized the importance of shared norms and values among community members, there lacks a unified conceptualization and measurement. In response, this study bridges insights from both online community research and traditional organizational culture literature to introduce the concept of online community culture. It further develops a measurement scale consisting of aggressive and supportive cultural elements, comprising nine items from the community member’s viewpoint. Through a series of studies involving several survey administrations, the scale demonstrates robust convergent, discriminant, and predictive validity. These findings have implications not only for advancing our understanding of the determinants of knowledge sharing in online communities, but also for assessing community culture and member composition, thereby facilitating sustainable online community operations.