A major obstacle in understanding the mechanism of ischemic stroke is the lack of a tool to noninvasively or minimally invasively monitor cerebral hemodynamics longitudinally. Here, we applied optical-resolution photoacoustic microscopy (OR-PAM) to longitudinally study ischemic stroke induced brain injury in a mouse model with transient middle cerebral artery occlusion (MCAO). OR-PAM showed that, during MCAO, the average hemoglobin oxygen saturation (sO 2) values of feeder arteries and draining veins within the stroke core region dropped ∼10% and ~34%, respectively. After reperfusion, arterial sO2 recovered back to the baseline; however, the venous sO 2 increased above the baseline value by ∼7%. Thereafter, venous sO2 values were close to the arterial sO2 values, suggesting eventual brain tissue infarction.