Mothers' and fathers' beliefs and reported behaviors regarding negative emotional expression and observed family negative emotion expressiveness were investigated as predictors of first-, third-, and fifth-grade children's self-reported peer competence. Parents' beliefs were related to their reported behaviors, and mothers accepted and encouraged greater expression of negative emotions in children than fathers did. Associations of children's peer competence with mothers' reported socialization behaviors and observed family negative expressiveness were curvilinear: moderately high levels of encouragement of children's negative emotional expression and moderate levels of family negative expressiveness were related to greater perceived peer competence in children. Further, an interaction between child grade and mothers' beliefs indicated that fifth graders with mothers who were more accepting of their expression of negative emotions reported higher peer competence than fifth graders whose mothers were less accepting. Findings have important implications for developing interventions and education for parents and children.