Background: Currently with the emergence of the Internet, patients have an opportunity to exchange social support online. However, little attention has been devoted to different dimensions of online social support exchanged in virtual support communities for patients with multiple sclerosis (MS). Methods: To provide a rich insight, the aim of this qualitative study was to explore and categorize different dimensions of online social support in messages exchanged in a virtual support community for patients with MS. A total of 548 posted messages created during one year period were selected using purposive sampling to consider the maximum variation sampling. Prior-research-driven thematic analysis was then conducted. In this regard, we used the Cutruna and Suhr’s coding system. The messages that could not be categorized with the used coding system were thematically analyzed to explore new additional social support themes. Results: The results showed that various forms of social support including informational, emotional, network, esteem and tangible support were exchanged. Moreover, new additional social support themes including sharing personal experiences, sharing coping strategies and spiritual support emerged in this virtual support community. Conclusion: The wide range of online social support exchanged in the virtual support community can be regarded as a supplementary source of social support for patients with MS. Future researches can examine online social support more comprehensively considering additional social support themes emerging in the present study.