Studies in the field of child welfare services have shown that children's externalizing problems are linked to the immediate social relationships in which they are embedded. However, most studies that examined this association focused on specific dyads or general social support, ignoring more diverse and complex patterns of relationships in which children are embedded. Therefore, this study used Social Network Analysis to analyze how compositional and structural properties of parents' personal networks predict externalizing problems of children in vulnerable family contexts. The sample consists of 70 parents who were enrolled in a home‐based family intervention in Switzerland. A hierarchical cluster analysis revealed three clusters based on the network composition: mixed, child‐oriented, and family of orientation. Child behavior problems were associated with the network clusters; school‐related problems, on the other hand, were additionally linked with support density in the personal networks of parents. The results show that children in vulnerable families are embedded in diverse network compositions and relational structures, which influence their externalizing problems in different ways.