This study examined the development of implicit race attitudes in American and Japanese children and adults. Implicit ingroup bias was present early in both populations, and remained stable at each age tested (age 6, 10, and adult). Similarity in magnitude and developmental course across these 2 populations suggests that implicit intergroup bias is an early-emerging and fundamental aspect of human social cognition. However, implicit race attitudes toward favored outgroups are more positive in older than in younger participants, indicating that “cultural prestige” enjoyed by a group moderates implicit bias as greater knowledge of group status is acquired. These results demonstrate (a) the ready presence, (b) early cultural invariance, and (c) subsequent cultural moderation of implicit attitudes toward own and other groups.