Technical Abstract: Large portions of energy-dense foods are one feature of obesity-promoting dietary environments. Entrée portion size has been shown to influence energy intake at meals by young children. The role of energy density (ED) in children’s response to portion size, however, is unknown. We aimed to test the effects of portion size and ED on children’s food and energy intakes at a meal. Participants were 53 (28 girls and 25 boys; 15 Hispanic, 20 black, 16 white, 2 other race) 5- to 6-y-old children [mean (+/-SD)body mass index percentile: = 61 +/- 28]. A 2 x 2 within-subjects design was used to manipulate entrée portion size (250 compared with 500 g) and ED (1.3 compared with 1.8 kcal/g). Fixed portions of other familiar foods were provided. Weighed intake, food preference, and weight and height data were obtained. Effects of portion size (P < 0.0001) and ED (P < 0.0001) on entree energy intake were independent but additive. Energy intake from other foods at the meal did not vary across conditions. Compared with the reference portion size and ED condition, children consumed 76% more energy from the entree and 34% more energy at the meal when served the larger, more energy-dense entree. Effects did not vary by sex, age, entree preference, or body mass index z score. These findings provide new evidence that portion size and ED act additively to promote energy intake at meals among preschool-aged children.