Introduction: Dietary energy-dense foods predispose to obesity and may be associated with risk of type 2 diabetes therefore, the aim of our study was to investigate the association between dietary energy density (DED) and the risk of type 2 diabetes. Materials and Methods: In this matched nested case-control study, 178 new onset cases of diabetes were selected from among participants of the Tehran Lipid and Glucose Study, and followed for over 9 years. Each case was randomly matched with 3 controls from among participants who had not developed diabetes. Dietary intakes were determined using a valid and reliable food frequency questionnaire. DED was calculated as energy intakes (kcal) from foods and beverages divided by the weight (grams) of foods. Results: The mean ages of participants were 43±6.5 and 44.5±12 years, in women and men respectively. Individuals with higher DED had higher calories, total fat, carbohydrate and processed meat intakes and lower fruit and vegetable intakes in men and women (P<0.05). Energy density was positively associated with incident diabetes in women, after adjustment for diabetes risk factors and total calorie intake (OR: 2.28, P trend=0.02) or total fat intake (OR: 2.15, P trend=0.03), an association which was not significant in men. Conclusion: In this nested case-control study, there was positive association between DED and risk of type 2 diabetes in women.