ABSTRACT Socially anxious children and adolescents have previously been found to have friends with similarly socially anxious, withdrawn behavioral characteristics. How peers might socialize social anxiety over time has, however, not been thoroughly investigated. We examined this in a sample of 834 youths (339 girls and 495 boys; M=14.29), followed for 3 years. We used the social network analysis software SIENA to analyze the data. The results showed that youths who were socially anxious were less popular and chose fewer friends in the network. They also tended to choose friends who were socially anxious, and over time they influenced each other into becoming more socially anxious—over and above other effects. Finally, girls' social anxiety was more influenced than boys' by their friends' social anxiety levels. The results showed the significance of looking at socially anxious youths' friendships over time and embedded in social networks.