This 3-year, longitudinal analysis examined the psychological and social correlates of adhering to gender-typed behaviors in friendships among boys during middle school in United States ("N" = 446, "M"[subscript age] = 11.37 years) and in China ("N" = 368, "M"[subscript age] = 12.20 years). Results indicated that boys did not differ by nationality in the mean levels or in the increase over time in adherence to gender-typed behaviors. Furthermore, adherence over time was associated with higher depressive symptoms, lower self-esteem, and lower friendship quality for boys in both countries. However, the associations between gender-typed behaviors and friendship quality and depressive symptoms were stronger for boys in the United States. Our study suggests that gender-typed behaviors play an important role in the well-being of youth in different parts of the world. (Contains 3 figures and 2 tables.)