Objectives: To examine the association between ethnicity, depression, quality of life, and diabetic control in Malaysian adolescents and young adults with type I diabetes mellitus. Methods: Fifty-two outpatients with type I diabetes (mean age 15.5 years) who attended a Diabetes Clinic were included. The level of HbA1c was the measure of diabetes control used (better control defined as HbA1c < 10%). Other variables were measured through questionnaires (e.g., depressive symptoms, quality of life), computerized diagnostic interviews (major depression), and medical records (e.g., demographic, family circumstances, compliance with treatment). Results: Ethnic Chinese youth showed better diabetic control than Malays and Indians (mean HbA1c 9.1%, 10.3%, and 11.0% respectively). Young people with better diabetic control (HbA1c < 10%) were more likely to have better quality of life and less likely to live in problematic families. When the cut-off for diabetic control was stricter (HbA1c ≤ 8%), the young person's compliance was the main predictor of poor control. Family problems were also associated with poor control but to a lesser extent. The initial association between poorer diabetes control and depression became non-significant when quality of life was taken into account. Conclusions: There are ethnic differences in juvenile diabetic control in this Malaysian sample which need to be understood further. Previous findings of an association between quality of life and glycemic control were verified but different definitions of good control showed different associations with individual and environmental variables. Clinicians' awareness and early intervention for psychosocial problems (for example, inadequate family support) could improve diabetes control.