Quantifying the impact of environmental conditions on the mechanical properties and performance of hot mix asphalt (HMA) materials is a necessary task to achieve high-quality pavement structures. Although the influence of temperature in the behaviour of these viscoelastic materials has been well determined, there is still a lack of information regarding the impact of moisture on the mechanical response of HMA. Studies in this direction should consider that under actual field conditions, these mixtures are usually in a partial saturation state. Within this context, this work evaluates the mechanical response of an HMA through the quantification of the axial tension, axial compression and shear moduli of the mixture, after subjecting it to different relative humidity environments. The experimental plan was conducted using the recently developed Hollow-Cylinder Tester for Asphalt Mixtures equipment, and the results demonstrate that partial saturation strongly influences the rheological properties of these mixtures.