Although relationship expectations are thought to influence all social interactions, little is known about the function of children's friendship expectations. This study examined the associations among children's friendship expectations and their behavior within their friendships, their friendship adjustment, and their socioemotional functioning. Third-grade through fifth-grade children (N = 499; 260 girls and 239 boys; M[subscript age] = 9.88 years) completed measures of their friendship expectations, friendship effort, friendship quantity, friendship satisfaction, loneliness, and fear of negative evaluation as an index of their social anxiety. Using structural equation modeling, higher friendship expectations were found to be associated with more positive friendship adjustment and better socioemotional functioning. Friendship effort mediated these associations. Despite mean-level gender differences in friendship expectations, friendship expectations functioned in largely similar ways for girls and boys. These findings suggest that it is adaptive for children to have high relationship standards for their friends. Implications for the development of friendship interventions are discussed.