Prosocial behavior is considered an important dimension of positive development. Although previous research suggests the quality of children's early relationships may influence prosocial behaviors, the specific contributions of mother, father and teacher to children's prosocial behavior have been less examined. This is a cross-sectional study that investigates (a) the combined associations between mother-, father- and teacher-child relationships, and prosocial behavior in 168 children aged 36-72 months, and (b) the mediating role of the teacher-child relationship in the association between the parent-child relationship and prosocial behavior. Results suggested a positive link between the quality of relationships with early caregivers and children's prosocial behavior. The quality of both father- and teacher-child relationships were found to have a direct association with children's prosocial behavior. The quality of the mother-child relationship was indirectly linked to children's prosocial behavior, via the teacher-child relationship. Results suggesting connections between multiple relational contexts were discussed based on the notion of internal working models proposed by attachment theory. Mothers' and fathers' contributions to children's prosocial behavior were also discussed considering differences on relational styles and changing roles of mothers and fathers from dual-earner families. (author abstract)