ABSTRACT Children’s relationships with adults (e.g. parents and teachers) and within-family relationships (e.g. parent–parent) are important drivers for the development of children’s social competence. The current study examined the contributions of adult–child relationships (parent–child and teacher–child) and parent–parent relationships to preschool children’s social competence. In addition, the moderating roles of teacher–child relationships between parent–child and parent–parent relationships, and children’s social competence were examined. Participants were parents and teachers of 127 children (M = 54.65, SD = 9.22 months) from Turkey. Parents reported on parent–child and parent–parent relationships and teachers reported on teacher–child relationships and children’s social competence. Hierarchical regression models accounting for the nesting structure of the data were run to test the hypotheses. Results showed that teacher–child closeness was positively and teacher–child conflict was negatively associated with children’s social competence. Parent–child and parent–parent relationships were not associated with children’s social competence. Teacher–child closeness moderated the association between parent–parent conflict and social competence. The findings highlight the importance of examining both parent–parent and teacher–child relationships in the prediction of children’s social competence.