Annually, an estimated 1 million patients undergo heart surgery worldwide. Unfortunately, stroke continues to be a frequent complication of cardiac surgery, with the specific cerebrovascular risk depending upon the particular surgical procedure performed. Neuroimaging has an integral role in the initial evaluation and management of patients who present with acute stroke symptoms following cardiac surgery. The aim of this paper is to review the role brain MRI has in detecting postoperative brain ischemia in these patients. Multimodal MRI--using diffusion-weighted MRI (DWI), perfusion-weighted MRI, and gradient-recalled echo imaging--has an excellent capacity to identify and delineate the size and location of acute ischemic strokes as well as intracerebral hemorrhages. This differentiation is critical in making appropriate treatment decisions in the acute setting, such as determining patient eligibility for thrombolytic or hemodynamic therapies. At present, DWI offers prognostic value in patients with strokes following cardiac surgery. Additionally, DWI could be a valuable tool for evaluating stroke preventive measures as well as therapeutic interventions in patients undergoing CABG surgery.