Ethnic‐racial socialization is a salient component of parenting in Black families. What is less clear is how Black families discuss ethnicity‐race and social inequalities with pubescent children. We examined associations between pubertal timing and ethnic‐racial socialization among mothers (Mage = 42) of Black (n = 286) and Black‐White biracial (n = 233) girls aged 9–12. Moderation by maternal stress about puberty was also examined. Results indicated mothers of Black girls who were stressed about puberty reported more preparation for bias; whereas both groups of mothers reported more cultural socialization. Early pubertal timing and high maternal stress about puberty predicted more cultural socialization among both groups and more egalitarian beliefs among only mothers of Black‐White biracial girls. The findings highlight the importance of ethnic‐racial socialization during puberty.