BACKGROUND: Adolescents with Type 1 diabetes (T1D) show less effective metabolic control than other age groups, partly because of biological changes beyond their control and partly because in this period of developmental transition, psychosocial factors can militate against young people upholding their lifestyle and medical regimens. Parents have an important role to play in supporting adolescents to self-manage their disease, but resultant family tensions can be high. In this study, we aimed to assess family functioning and adolescent behaviour/ adjustment and examine the relationships between these parent-reported variables and adolescent metabolic control (HbA1c), self-reported health and diabetes self-care. METHOD: A sample of 76 parents of Australian adolescents with T1D completed the Child Health Questionnaire -Parent form. Their adolescent child with T1D provided their HbA1c level from their most recent clinic visit, their self-reported general health, and completed a measure of diabetes self-care. RESULTS: Parent-reported family conflict was high, as was disease impact on family dynamics and parental stress. Higher HbA1c (poorer metabolic control) and less adequate adolescent self-care were associated with lower levels of family functioning, more adolescent behavioural difficulties and poorer adolescent mental health. CONCLUSIONS: The implication of these findings was discussed in relation to needs for information and support among Australian families with an adolescent with T1D, acknowledging the important dimension of family functioning and relationships in adolescent chronic disease management.