Cardiovascular disease (CVD) is the leading cause of death in the United States, with 70% of CVD mortalities the result of sequelae of atherosclerosis. An urgent need for enhanced delineation of vulnerable plaques has catalyzed the development of novel atherosclerosis imaging strategies that use X-ray computed tomography, magnetic resonance and ultrasound modalities. As suggested by the pathophysiology of plaque development and progression to vulnerability, insight to the focal material, i.e., mechanical, properties of arterial walls and plaques may enhance atherosclerosis characterization. We present acoustic radiation force impulse (ARFI) ultrasound in application to mechanically characterizing a raised focal atherosclerotic plaque in an iliac artery extracted from a relevant pig model. ARFI results are correlated to matched immunohistochemistry, indicating elastin and collagen composition. In regions of degraded elastin, slower recovery rates from peak ARFI-induced displacements were observed. In regions of collagen deposition, lower ARFI-induced displacements were achieved. This work demonstrates ARFI for characterizing the material nature of an atherosclerotic plaque.