Research has shown inconsistent relationships between social anxiety and time spent on Facebook, possibly because Facebook’s many activities vary in degree of social interactivity. We examined the relationships between social anxiety, anxiety on Facebook, and social Facebook use. A multiple regression predicting social Facebook use revealed an interaction. Participants with high anxiety on Facebook and high social anxiety reported more frequent social Facebook use than those with high anxiety on Facebook and low social anxiety. A second multiple regression predicting social anxiety showed a suppression effect, indicating that social Facebook use predicts social anxiety only once anxiety on Facebook has been accounted for. These findings suggest that anxiety on Facebook clarifies the relationship between social anxiety and social Facebook use.