Socialization and individual differences were examined as antecedents of moral motivation in representative samples of 15-year-old adolescents (N = 1,258; 54% female) and 21-year-old young adults (N = 584; 53% female). The adolescents' primary caregivers (N = 1,056) also participated. The strength of moral motivation was rated by participants' responses to two hypothetical moral dilemmas in terms of action decisions, emotion attributions, and justifications. Socialization was measured by the perceived quality of friendship, parent-child relationships, and educational background. The importance attached to social justice and various personality traits were also assessed. Adolescents' moral motivation was positively associated with the quality of their parent-child relationship and the importance of social justice. Young adults' moral motivation was predicted by the perceived quality of friendships, the importance of social justice, and agreeableness. For both groups, moral motivation was greater in females. The theoretical implications of the findings for the development of moral motivation are discussed.