Online trading has now become the prevalent form of stock market investing. With a large percentage of investors now online, understanding how they make use of social media to share and gather information is of major interest to service providers, regulators, researchers and to investors themselves. Previous studies have explored public online investor networks such as stock forums, but few studies have investigated investors’ private online social networks. This paper reports on a qualitative study that interviewed 26 online investors about the various forms of social networks they participate in. Some online investors continue to rely on their private, offline networks of family and friends for information and advice. Other investors have taken their social networks online, but these online networks are still private. While investors do participate in public stock forums, it was also found that private social networks exist within these public virtual communities. Forum members get to know other members outside of the forums and form personal relationships. Such private social networks are not visible to outsiders.