Online communities now reach various aspects of people’s work and life; and both practitioners and researchers have recognized their importance. However, among the tens of thousands of online communities, a considerable portion of them gradually become lifeless, with little ongoing conversation and few active members. Since online communities largely rely on members’ participations to generate benefits, it is important to identify the behaviors that contribute to community sustainability. Specifically, the research questions are: 1) Besides knowledge contribution, what are the behaviors contributing to online community sustainability? 2) What is the nature of these behaviors? How do they benefit communities? Comparing online communities with organizations and referring to Organization Citizenship Behaviors (OCB), we conceptualize the benefiting creation behaviors as Online Community Citizenship Behaviors (OCCB), which have the following characteristics: 3) Discretionary 4) Beyond personal needs gratification 5) Promote the effective functioning of the online community We then identify the dimensions of OCCB, viewing online communities as complicated social entities which people go to with various needs to be fulfilled. Previous IS research mainly focuses on people’s information needs and examine knowledge sharing. Referring to social psychology studies on human needs and small group interaction analysis, we highlight that people also have social emotional needs, and argue for the importance of social emotional support on community sustainability. Behaviors offering social emotional support contribute to community relationship building, help to attract new members, and attract posts asking for social emotional support. We also examine behaviors related with community norm development and maintenance, such as recognizing other’s contribution, discouraging inappropriate behaviors. These behaviors cultivate community reciprocity norm and a friendly social atmosphere. They create strong bonding among members, retain members, and encourage members to contribute. We also note community participants may leverage other Internet platforms, such as personal blogs, to promote the community. Specifically, members’ recommendations on other platforms may generate publicity for the community and help the community to attract new users, hence we include cross platform community promotion in OCCB. Overall speaking, how to make online community sustainable is a question of both practical and theoretical interest. We address this question through investigating the benefit creating behaviors, i.e. OCCB. The study goes beyond knowledge contribution, and highlights behaviors related with social emotional needs gratifying, group norms forming, and group publicity. We propose that OCCB have positive influence on membership size, attracting posts seeking knowledge and social support, and hence make the community more influential and sustainable in the topical area; and we suggest ways to help community develop sustainably.