In general, replacement of saturated fat with monounsaturated and polyunsaturated fat reduces the risk of type 2 diabetes, with the evidence stronger for polyunsaturated fat. However, recent research studies have highlighted the importance of the source of dietary fat in prevention of type 2 diabetes. For example, saturated fats found in dairy products are associated with a reduction in risk in large epidemiological studies. Similarly, while polyunsaturated fats in vegetable oils and nuts appear to reduce the risk of type 2 diabetes, polyunsaturated fats in fish do not. This article will review the evidence for dairy products and fish in prevention of type 2 diabetes, with attention paid to risk factors such as insulin sensitivity, secretion and adiposity. The evidence suggests that consumption of low-fat dairy products can protect against type 2 diabetes, while the effect of full-fat dairy appears to be neutral. Oily and white fish have no independent effect on the risk of type 2 diabetes but their consumption is associated with a healthy body weight.