Enriched environments may moderate the effect of genetic factors on prosocial leadership (gene-environment interaction, G × E). However, positive environmental experiences may also themselves be influenced by a genetic disposition for prosocial leadership (gene-environment correlation, rGE). Relating these processes to friendships, the present study examined (a) whether children with a genetic disposition for prosocial leadership possess a greater number of reciprocal friends (rGE) and (b) whether the number of reciprocal friends interacts with the effect of genetic factors on children's prosocial leadership (G × E). The sample comprised 275 twin pairs assessed in Grade 1 (mean age 84.7 months). Reciprocal friendship and prosocial leadership behavior were measured via peer nominations. Consistent with rGE, a genetic disposition for prosocial leadership was related to an increased likelihood of friendship. Moreover, consistent with a compensation process, environmental influences played a stronger role than genetic influences in prosocial leadership when children had many friends.