Ischemia and reperfusion contribute to substantial organ damage in transplantation. Clinically feasible measures for the prevention thereof are scarce. We tested whether rinsing rodent hearts with the antioxidant bilirubin ameliorates ischemia reperfusion injury (IRI). Left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDevP), rate per pressure product (RPP), coronary flow, maximum (+dP/dt) and minimum (−dP/dt) rate of contraction were analyzed in Lewis rat hearts rinsed with bilirubin prior to reperfusion on a Langendorff apparatus after 12 h of cold ischemia. In vivo, isogenic C57Bl/6 mouse hearts rinsed with bilirubin were transplanted after 12 h of cold ischemia. Cardiac function and apoptosis were assessed 24 h after reperfusion. Heart lysates recovered 15 min after reperfusion were probed for the total and the phosphorylated forms of extracellular signal-related protein kinases (ERK), JNK, p38-MAPK, and Akt. In isolated perfused hearts, bilirubin rinse resulted in significantly lower LVEDP and improved LVDevP, RPP, coronary flow, +dP/dt and −dP/dt. In vivo, after reperfusion, all mitogen-activated protein kinases (MAPKs) were suppressed significantly by bilirubin pretreatment. Bilirubin rinse improved cardiac scores (3.4 ± 0.5 vs. 2.0 ± 1.0 in controls, P < 0.05) and significantly suppressed apoptosis. Ex vivo administration of bilirubin to heart grafts prior reperfusion ameliorates IRI and provides a simple and effective tool to ameliorate outcome in heart transplantation.