OBJECTIVE: This study investigated whether intimacy and autonomy in mother-daughter interactions and relational aspects of the self are associated with metabolic control in adolescent girls with type 1 diabetes. RESEARCH DESIGN AND METHODS: This cross-sectional study included 88 girls with diabetes (mean age 14.9 +/- 2.2 years, diabetes duration 7.1 +/- 3.9 years, and HbA1c 8.9 +/- 1.6%) from the Diabetes Clinic at the Hospital for Sick Children in Toronto and their mothers. Teens completed a self-report measure assessing self-concept in eight domain-specific areas. Mothers and daughters engaged in a 7-min, videotaped, problem-solving task involving a diabetes-related conflict issue. Interactions were rated using a macroanalytic rating system to assess intimacy and autonomy in parent-teen relationships. Metabolic control was measured using HbA1c. RESULTS: Self-concept in domains of perceived behavioral conduct (P=0.003), social acceptance (P=0.03), romantic appeal (P=0.03), and close friendships (P=0.04) independently predicted HbA1c levels, together accounting for 30% of the variance. Also, the experience of emotional closeness (i.e., intimacy) rather than separateness (i.e., autonomy) in mother-daughter relationships was associated with lower HbA1c (P=0.03). CONCLUSIONS: Relational aspects of the self and the experience of emotional closeness in relationships are associated with metabolic control in adolescent girls. Efforts to improve metabolic control in girls should include enhancing the self-concept and the experience of relatedness in familial, peer, and patient-caregiver relationships.