Early childhood relationships with teachers, parents, siblings, and peers are foundational factors for later social functioning. High rates of childhood aggression have been associated with negative developmental consequences, however, the associations between child aggression on the quality of these formative relationships have not been studied extensively. In a sample of young children attending preschool (N = 114, Mage = 46.27 months, SD = 9.94, 40% girls), this study investigated associations between early childhood relational and physical aggression and the quality of concurrent teacher‐child and parent–child closeness and conflict, sibling relationship quality, and positive peer interactions and peer rejection. Early childhood relational and physical aggression was associated with negative teacher–child relationships, and this was true for boys and girls. Differential patterns of prediction were found for relational and physical aggression on the other relationship variables. Relational aggression strongly predicted more positive peer interactions, whereas physical aggression predicted fewer positive peer interactions and greater peer rejection. Early childhood relational aggression predicted higher levels of teacher‐child closeness, whereas physical aggression predicted lower levels of teacher–child closeness and fewer positive sibling interactions. These findings challenge common perceptions that aggression is negatively associated with relationship quality. Notably, relational aggression relative to physical aggression may be associated with some favorable relationship outcomes. We did not find support for an additive model of aggression whereby children who were both relationally and physically aggressive (co‐morbid) were at higher risk for negative relationship quality. Implications of these findings for future research and prevention and intervention are discussed.