© 2017 Informa UK Limited, trading as Taylor & Francis Group. Background: Prior to heart transplantation, static storage of donor hearts is currently limited to 4–5 h, despite profound hypothermia (4–8 °C). Because heart transplantation is an emergency procedure, improved protection to extend safe storage duration would be advantageous. We investigated whether the naturally respiratory pigment HEMO2life®, which is effective at hypothermia for the passive release of oxygen via oxygen gradient, could improve long-term preservation. Methods: Isolated Langendorff-perfused rat hearts (n = 12/group) were equilibrated (20 min) and function (left ventricular developed pressure: LVDP) measured by intraventricular balloon before arrest with cold (7.5 °C) Celsior® solution, either alone (control) or with the addition of HEMO2life® (Hemarina SA, Morlaix, France) at 1 g/L. Cold storage lasted 8 h prior to reperfusion (60 min) and recovery (as % of pre-ischemic function) was assessed. Hearts (minced and homogenized) were also assessed by TTC staining as a measure of viability and two hearts from each group were sliced and assessed by TTC staining for infarct size. Values are expressed as mean ± standard error of mean and analyzed by Student’s t-test. Results: Hearts recovered rapidly in both groups to a plateau by 20 min of reperfusion; control and HEMO2life® final recovery (60 min) was 45 ± 2% and 57 ± 1% (P < 0.05) respectively. Left ventricular end-diastolic pressure recovered to a similar extent in both groups (between 31 to 35 mmHg), as did heart rate (final recovery between 84 to 89% pre-ischemic value); however, coronary flow was significantly (P < 0.05) higher in HEMO2life® group (7.5 ± 0.7 ml/min) compared to control (5.4 ± 0.4 ml/min). Viability and infarct size measurements were similar between groups. Conclusion: The addition of the natural oxygen releasing pigment HEMO2life® to Celsior® preservation solution significantly improved post-ischemic recovery of heart function. This additive may have major therapeutic potential for clinical heart transplantation.