Individuals with other-race friends are perceived to identify less strongly with their racial in-group than are individuals with same-race friends. Using the reverse-correlation technique, we show that this effect goes beyond perceptions of social identification, influencing how people are mentally represented. In four studies with Black and White American participants, we demonstrate a “racial assimilation effect”: Participants, independent of their own race, represented both Black and White targets with other-race friends as phenotypically more similar to the respective racial out-group. Representations of targets with racial out-group friends were subsequently rated as more likely to engage in social action supportive of the racial out-group. Out-group targets with other-race friends were represented more favorably than out-group targets with mostly same-race friends. White participants had particularly negative representations of in-group members with mostly Black friends. The present research suggests that individuals’ social networks influence how their race and associated traits are mentally represented.