Increased employee mobility and the widespread use of teams underline the importance of understanding the socialization of newcomers into groups. Applying the theory of cooperation and competition, this study experimentally investigated the relationship between team climate and newcomer socialization and performance. We found that a cooperative, in comparison to a competitive or independent team climate strengthened the relationship and interaction between newcomers and the other team members. Thereby, this facilitated newcomer socialization. Copyright © 2008 the Authors.