This paper demonstrates that linguistic similarity predicts network tie formation and that friends exhibit linguistic convergence over time. Study 1 analyzes the linguistic styles and the emerging friendship network in a complete cohort of 285 students. Study 2 analyzes a large-scale dataset of online reviews. Across both studies, we collected data in two waves to examine changes in both friendship networks and linguistic styles. Using the LIWC linguistic framework, we analyze the text of students’ essays and of 1.7 million reviews by 159,651 Yelp reviewers. We find that similarity in linguistic style corresponds to higher likelihood of friendship formation and persistence, and that friendship ties, in turn, correspond with a convergence in linguistic style. We discuss the implications of the co-evolution of linguistic styles and social networks, which contribute to the formation of relational echo chambers.