The relationship between social sharing of emotions, social networks and social ties is an ongoing topic of research. Such sharing of emotions occurs frequently in “social awareness streams” platforms like Twitter and Facebook. We use Twitter to address research questions about the association of properties of a user’s network, such as size and density, with expression of emotion in the user’s Twitter posts. Our analysis suggests that expression of emotion can explain some of the variance in users’ Twitter networks, and that the use of emotion in interactions between users is a strong explaining factor. Author Keywords Social media, Twitter, social networks, emotions ACM Classification Keywords H.4.3 [Information Systems Applications]: Communication Applications; General Terms Social Networks, Emotions, Social Media