Close friendships become increasingly prevalent during late childhood and early adolescence. While these friendships can provide general positive outcomes, they also have the possibility of generating negative emotions, such as jealousy. This may be especially true when the child perceives closeness between their friend and a third person. This link between perceptions and jealousy has been explored in the romantic literature, but not in the friendship literature. The purpose of the present study was to directly test this link between friendship jealousy and perceptions. It was hypothesized that children who perceived higher intimacy between the best friend and third child would be more prone to jealousy. It was also hypothesized that sex, self-esteem, and a child’s own closeness would independently moderate this link. The results showed that, contrary to the hypothesis, the more children perceived closeness between their best friend and a third person, the less jealous they became. In addition, sex and self-esteem were significantly related to jealousy, but these variables did not moderate the relation between perceptions and jealousy. Although own closeness was only marginally related to jealousy, there was a significant sex by closeness interaction, such that boys had an increase in jealousy the closer they were to their friend. Further analyses did show significant age differences, with older children viewing less closeness and becoming less jealous. Furthermore, children in this study appeared to be fairly accurate in judging the closeness of their friend with another peer. These findings uniquely contribute to the friendship literature by highlighting the importance of perceptions in friendship jealousy. Implications of these findings and future directions are discussed.