The stiffness behavior of an idealized asphalt mixture at the different air void levels was investigated in this paper. The asphalt mixture was modeled with the discrete element modeling (DEM) approach by randomly generated air voids in two dimensions (2D) and three dimensions (3D). Air voids were calculated within the DEM model to meet the specific air void level (i.e. 4%, and 10%). Sixteen different 2D idealized models were generated with 4% and 10% air void levels. A 3D idealized model was generated using the 16 2D models. Then the 16 replicates of the 3D models were prepared with 4% and 10% air void levels. Both 2D and 3D models were used to compute the stress-strain response under compressive loads. The moduli of specimens were computed from the stress-strain curve. The result showed modulus decreased with air void increased. The 3D model predicted higher modulus than the 2D models. When air voids increased from 0% to 10%, the modulus decreased 30% on the 3D models and 48% on the 2D models. When comparing modulus prediction of 2D and 3D models, it was found that, at 0% air void level, the prediction was the same for both 3D and 2D. However, at 10% air void levels, 3D models yielded 26% higher modulus than the 2D models. It was found that the modulus deviation on the 3D models was much lower than the 2D models.