Coronary artery disease is the leading cause of death and disability worldwide. In patients with acute coronary syndromes, timely and effective myocardial reperfusion by percutaneous coronary intervention is the primary treatment of choice to minimize the ischemic injury and limit the size of the myocardial infarction (MI). However, reperfusion can itself promote cardiomyocyte death, which leads to cardiac dysfunction via reperfusion injury. The molecular mechanisms of ischemia-reperfusion (IR) injury are not completely understood and new drug targets are needed. Recently, we reported that cardiac troponin I-interacting protein kinase (TNNI3K), a cardiomyocyte-specific kinase, promotes IR injury via profound oxidative stress, thereby promoting cardiomyocyte death. By using novel genetic animal models and newly developed small-molecule TNNI3K inhibitors, we demonstrated that TNNI3K-mediated IR injury occurs through impaired mitochondrial function and is in part dependent on p38 MAPK. Here we discuss the emerging role of TNNI3K as a promising new drug target to limit IR-induced myocardial injury. We will also examine the underlying mechanisms that drive the profoundly reduced infarct size in mice in whichTNNI3Kis specifically deleted in cardiomyocytes. Because TNNI3K is a cardiac-specific kinase, it could be an ideal molecular target, as inhibiting it would have little or no effect on other organ systems, a serious problem associated with the use of kinase inhibitors targeting kinases that are more widely expressed. (Circ J 2014; 78: 1514–1519)