Aging is accompanied by neurodegeneration, which affects the cerebral biomechanical properties. We investigated the impact of age and sex on mouse brain stiffness using magnetic resonance elastography (MRE). Repeated MRI and MRE exams were performed on 5 male and 5 female healthy C57BL/6 mice over 14 months. A significant decrease of the viscoelastic modulus |G*| was observed, while the phase angle Y remained unaltered. Grey and white matter exhibited significant differences in |G*| and Y. Sex differences were observed in the cortex at 11 months. This is relevant for future cerebral MRE studies on mice.