Adenosine signaling has been implicated in cardiac adaptation to limited oxygen availability. In a wide search for adenosine receptor A2b (Adora2b)-elicited cardioadaptive responses, we identified the circadian rhythm protein period 2 (Per2) as an Adora2b target. Adora2b signaling led to Per2 stabilization during myocardial ischemia, and in this setting, Per2 -/- mice had larger infarct sizes compared to wild-type mice and loss of the cardioprotection conferred by ischemic preconditioning. Metabolic studies uncovered a limited ability of ischemic hearts in Per2 -/- mice to use carbohydrates for oxygen-efficient glycolysis. This impairment was caused by a failure to stabilize hypoxia-inducible factor-1Î ± (Hif-1Î ±). Moreover, stabilization of Per2 in the heart by exposing mice to intense light resulted in the transcriptional induction of glycolytic enzymes and Per2-dependent cardioprotection from ischemia. Together, these studies identify adenosine-elicited stabilization of Per2 in the control of HIF-dependent cardiac metabolism and ischemia tolerance and implicate Per2 stabilization as a potential new strategy for treating myocardial ischemia.