In this study, we examined the diet of 149 males and 147 females of Eutropis macularius from Thua Thien Hue Province, central Vietnam using a nonlethal stomach-flushing technique. The prey items of E. macularius composed of Araneae, Insecta (Blattodea, Coleoptera, Hymenoptera, Isoptera, Odonata, and Orthoptera), Mollusca (Philomycidae), and plant materials. The most important prey items were insect larvae, hymenopterans (including ants), grasshoppers, and termites, for both sexes in three populations. Plant materials were also found in the stomach of E. macularius with an index of relative importance of 7.19%, suggesting that E. macularius is an omnivorous species. However, the dominant prey categories of E. macularius were insects, including insect larvae, hymenopterans, grasshoppers, and termites, with many small, sedentary, clumped prey items. Simpson’s heterogeneity index of skinks from three populations from Bach Ma National Park as well as from Aluoi and Huong Tra districts were 10.07, 7.85, 3.94, respectively. Eutropis macularius showed significant positive correlations between mouth width (MW) and prey width (P = 0.001) and between MW and prey volume (P 0.0001). There are significant positive correlations between snout-vent length (SVL) and prey sizes consumed: between SVL and prey length, P 0.0001; SVL and prey width, P 0.0001; and between SVL and prey volume, P 0.0001. These results indicated that SVL and MW are the limiting factors on the size of prey consumed in this skink.