Rupture of carotid atherosclerotic plaques is one of the major causes of stroke. Assessment of rupture risk (i.e., vulnerability) is important to prevent the occurrence of ischemic events. Ultrasound-based carotid elastography measures the motion and deformation of the plaque tissue induced by the pulsation of blood pressure, so as to infer the elasticity or composition distribution of the plaque for risk assessment. In vivo validation of carotid elastography is still limited. In this study, magnetic resonance imaging (MRI) was used as an in vivo reference standard to evaluate the capability of carotid elastography in detecting vulnerable plaques. The results demonstrated that the magnitude of the plaque strain rate and the heterogeneity of the elasticity distribution of the plaque tissue derived from texture analysis on plaque strain rate images can be used to effectively distinguish between the stable and vulnerable plaques. The inter-operator reproducibility of carotid elastography for identifying vulnerable carotid plaques is also validated.