The aim of the current study was twofold: (1) to investigate the concurrent and longitudinal links in 3–5-year old children between the antisocial and prosocial tendencies of the children's nominated best friends and children's own antisocial and prosocial behavior; and (2) to investigate age and gender as possible moderators of these links. As hypothesized, the study found that children's level of antisocial and prosocial behavior was significantly related to the levels of antisocial and prosocial behavior demonstrated by their nominated best friends. The type and magnitude of these associations varied according to behavior type. An unexpected finding was the relatively large number of children who did not nominate any best friends at T1. Contrary to our hypothesis, there were no main effects of gender in the current study. However, gender was found to moderate concurrent links between nominated best friends’ behavior and target child's antisocial behavior—this link was found for boys only. In contrast, age of the target child did not moderate the associations between nominated best friends’ behavior and children's own behavior. A discussion of these findings and their possible implications follows.