Aims: Evidence strongly suggests that depression is a common complication of Type 2 diabetes mellitus. However, there is considerable room to improve the effectiveness of pharmacological antidepressant agents, as in only 50-60% of the depressed subjects with diabetes does pharmacotherapy lead to remission of depression. The aim of the present paper was to review whether polyunsaturated fatty acids (PUFA) of the ω-3 family could be used for the prevention and treatment of depression in Type 2 diabetes. Methods: MEDLINE database and published reference lists were used to identify studies that examined the associations between ω-3 PUFA and depression. To examine potential side-effects, such as on glycaemic control, studies regarding the use of ω-3 supplements in Type 2 diabetes were also reviewed. Results: Epidemiological and clinical studies suggest that a high intake of ω-3 PUFA protects against the development of depression. There is also some evidence that a low intake of ω-3 is associated with an increased risk of Type 2 diabetes, but the results are less conclusive. Results from randomized controlled trials in non-diabetic subjects with major depression show that eicosapentaenoic acid is an effective adjunct treatment of depression in diabetes, while docosahexanoic acid is not. Moreover, consumption of ω-3 PUFA reduces the risk of cardiovascular disease and may therefore indirectly decrease depression in Type 2 diabetes, via the reduction of cardiovascular complications. Conclusions: Supplementation with ω-3 PUFA, in particular eicosapentaenoic acid, may be a safe and helpful tool to reduce the incidence of depression and to treat depression in Type 2 diabetes. Further studies are now justified to test these hypotheses in patients with Type 2 diabetes. © 2005 Diabetes UK.