The study examined how 'transition readiness' skills develop from relationship processes with parents, friends, and healthcare providers. During their senior year of high school and one year later, participants (N = 217) with type 1 diabetes completed measures of transition readiness skills (Self-Management; Self-Advocacy), adherence, HbA1c, and relationships with providers (patient-centered communication), parents (monitoring/knowledge), and friends (knowledge/helpfulness) surrounding diabetes. Self-Management skills increased across time. Higher friend knowledge/helpfulness during emerging adulthood was associated with increased Self-Management skills. Adherence improved when relationships with providers and friends matched transition readiness skills, indicating that these relationships may facilitate transition skills in early emerging adulthood.