Diabet. Med. 27, 798–803 (2010) Objectives  To investigate whether diabetes‐specific emotional distress mediates the relationship between depression and glycaemic control in patients with Type 1 and Type 2 diabetes. Research design and methods  Data were derived from the baseline assessment of a depression in diabetes screening study carried out in three tertiary diabetes clinics in the Netherlands. Most recent glycated haemoglobin (HbA1c) measurement was obtained from medical records. The Centre for Epidemiologic Studies Depression Scale (CES‐D) and Problem Areas in Diabetes scale (PAID) were used to measure depression and diabetes‐specific emotional distress respectively. Linear regression was performed to examine the mediating effect of diabetes–distress. Results  Complete data were available for 627 outpatients with Type 1 (n = 280) and Type 2 (n = 347) diabetes. Analyses showed that diabetes–distress mediated the relation between depression and glycaemic control and not differently for both disease types. Post‐hoc analyses revealed that patients depressed and distressed by their diabetes were in significantly poorer glycaemic control relative to those not depressed nor distressed (HbA1c 8.7 ± 1.7 vs. 7.6 ± 1.2% in those without depressive symptoms, 7.6 ± 1.1% in depressed only and 7.7 ± 1.1% in the distressed only, P < 0.001). Depressed patients without elevated diabetes‐distress did not show a significantly increased risk of elevated HbA1c. Conclusions  In explaining the association between depression and glycaemic control, diabetes‐specific emotional distress appears to be an important mediator. Addressing diabetes‐specific emotional problems as part of depression treatment in diabetes patients may help improve glycaemic outcomes.