Because of the difficulties associated with the generation of finite element meshes based on X-ray computed tomography scans and with the extraordinary computational demands in performing three-dimensional (3-D) finite element analyses, past modeling efforts have focused primarily on two-dimensional representations of asphalt mixtures and have placed no emphasis on the inclusion of the air voids network in the body of an asphalt concrete specimen. A 3-D micromechanical moisture damage model has been developed and implemented in the finite element system CAPA-3D capable of addressing individually the three main phases of asphalt concrete: aggregate, mastic, and air voids. The 3-D finite element meshes of different types of asphalt mixtures were generated on the basis of X-ray scans. By means of CAPA-3D, the significance of the air voids structure in the development of moisture damage in asphalt concrete specimens was demonstrated. Availability of the model enables evaluation and ranking of the contribution of the characteristics of the individual mixture components to the overall mixture moisture resistance.