While it’s logical to assume that children who are mean have friendships characterized by growing strife and that children who are nice report little of the same, these assumptions haven’t been tested in real-world friendships. A study of elementary-school children is the first to examine the extent to which being ‘nice’ and being ‘mean’ shape changes in friend perceptions of their relationship. Results confirm the widespread assumption that one child’s behavioral traits drive the other child’s friendship experiences.