People with multiple sclerosis often experience depression and anxiety, negatively affecting their quality of life, especially their social life. Peer support, whether in person or online, could improve social connection and coping. Online peer support allows people to engage from their home at a time that suits them. We sought to explore the benefits and challenges of online peer support and to identify successful elements of online peer support for people with multiple sclerosis. Using the narrative synthesis method, 6 databases were searched in April 2020 for articles published between 1989 and 2020; the search was updated in May 2022. The quality of the included studies was assessed using the Critical Appraisal Skills Programme qualitative research checklist and the Downs and Black checklist. Of 10,987 unique articles identified through the database search, 11 were included. Benefits of online peer support included sharing information and experiences and emotional support. Successful elements included having a dedicated space to save information and the convenience of online peer support. Challenges included verification of information and the lack of nonverbal communication. Online peer support can help those unable to access in-person support groups and can reduce the risk of social isolation. However, multiple sclerosis symptoms may make it difficult to use technological devices. Research is needed to further explore potential barriers to online peer support.