Cardiac procedures carry a higher perioperative risk than other operations for major adverse cardiovascular events and kidney injury, especially since patients with multiple comorbidities have been accepted as candidates for undergoing surgical treatment. Dexmedetomidine (DEX) is an alpha-2 agonist and has been widely used as an adjuvant anesthetic in clinical anesthesia for many different types of operations, including cardiac surgery. While it can be associated with bradycardia as well as hypotension in hypovolemic patients, DEX has been shown to reduce surgical complications like atrial fibrillation (Afib) and acute kidney injury (AKI), and is associated with an improved survival rate. In this review, we discuss the effect of using perioperative DEX on hemodynamics, arrhythmia, AKI, cognitive function, and surgical outcome in patients undergoing cardiac surgery both with and without cardiopulmonary bypass (CPB), and we review the mechanisms.