OBJECTIVE: To examine whether spontaneous causal attributions for blood glucose events were associated with blood glucose control (HbA(1c) [A1C]), self-management, and adjustment to diabetes. RESEARCH DESIGN AND METHODS: A total of 62 adults (31 female) with type 1 diabetes, recruited from a diabetes specialist clinic, with a mean age of 42.3 years and a mean illness duration of 19.6 years, were interviewed about the onset, history, course, and management of their diabetes. Spontaneous causal attributions for fluctuations in blood glucose level were extracted from the interviews and coded in accordance with the Leeds Attributional Coding System. Participants completed questionnaire measures of anxiety, depression, and appraisal of diabetes. Glycemic control (A1C) at the time of interview and 1 year later was extracted from notes. RESULTS: Participants who made proportionally more personal, or idiosyncratic, explanations for blood glucose fluctuations or events (such as hypoglycemic episodes) had higher A1C levels at time 1 and 1 year later and were judged to manage their diabetes less well. Furthermore, the association between personal attributions and A1C was partly accounted for by self-management behavior. Participants who made personal and stable attributions appraised their diabetes more negatively. CONCLUSIONS: Clinicians should be sensitive to patients' causal explanations for blood glucose events. Helping patients consider alternative explanations may produce benefits in terms of better management and control of diabetes.