In this study, we assessed the mechanical response of samples from human atherosclerotic diseased media and fibrous cap via uniaxial tensile testing. Results show a pronounced hysteresis phenomenon caused by viscoelasticity during the loading-unloading process. An inverse analysis method with finite element modeling was employed to identify the material parameter values for a viscoelastic anisotropic (VA) constitutive model through matching simulation predictions of load-displacement curves with experimental measurements. The identified material parameter values can be used in simulation studies of diseased human carotid arteries, including investigations of inflation processes associated with stenting or angioplasty.