The performance of asphalt mixtures is significantly affected by the viscoelastic properties of their mastic phase. The analytical approaches used to predict the mastic’s properties from its composition and constituents are limited in their accuracy as well as potential to handle non-linear material behaviour. An alternative micromechanical finite element modelling approach to calculate the mastic’s master curve from the binder and filler phase properties is presented in this paper. In the model, the mastic’s representative volume element is generated and it consists of a linear viscoelastic bitumen matrix and elastic spherical filler particles. In order to validate the model, shear relaxation moduli of bitumen and bitumen-filler mastics are measured at temperatures between −10 to 80 °C. For the two mastic materials characterized experimentally, micromechanical models are set-up and their capability to capture the measured response is evaluated and compared with the existing analytical solutions. The obtained results indicate that the proposed finite element modelling approach is advantageous as compared to the analytical solutions, as it both allows predicting mastic’s properties over wider temperature, frequency and material range as well as results in a better agreement with the measurements.