This study evaluates the influence of constituent properties on the mechanical behavior of asphalt mixtures. A computational microstructure model is used to simulate the overall behavior of the mixtures based on individual constituent properties. The heterogeneous mixtures are composed of linear elastic coarse aggregate particles that are embedded into a viscoelastic fine- Aggregate asphalt matrix phase. To properly model the mechanical behavior of the composite, other complex mixture characteristics, such as geometrical properties of the aggregate particles and rate-dependent fracture characteristics of the fine aggregate asphalt matrix are taken into account in the model. Simulations are performed to demonstrate the ability of the model to identify the influence of mix constituents and design factors such as stiffness, volume fraction, and fracture characteristics on the overall mechanical behavior of the mixtures. Even if extra work is required to refine the model, the results demonstrate that carefully-developed computational microstructure models, such as the one presented herein, represent a promising strategy to model the complex behavior of asphalt mixtures in a scientifically-sound and efficient manner.