The relation between children’s trust beliefs and trusting behavior in peer interaction was examined. One hundred and 5 Italian children (54 boys; mean age = 10 years-7 months) completed standardized scales of reliability (i.e., promise keeping) trust beliefs in parents and peers. The children participated in mixed-motive interactions with classmates which assessed behavior-dependent reliability trust on peers. The children’s reliability trustworthiness towards peers/classmates was assessed by peer reports. The SEM analyses supported the hypothesized model by showing: (1) a path between trust beliefs in parents and trust beliefs in peers; (2) paths between both types of trust beliefs and behavior-dependent trust on peers; (3) a path between behavior-dependent trust in peers and trustworthiness towards peers. Trust beliefs in peers were found to mediate the relation between trust beliefs in parents and behavior-dependent trust in peers. The findings yielded support for the basis, domain, and target trust framework and attachment theory.