Extrahepatic tissues which oxidise ketone bodies also have the capacity to accumulate them under particular conditions. We hypothesised that acetyl-CoA accumulation and altered redox status during low-flow ischaemia would support ketone body production in the heart. Combining a Langendorff heart model of low-flow ischaemia/reperfusion with LC-MS/MS, we show that β-hydroxybutyrate (β-OHB) accumulated in the ischaemic heart to 23.9 nmol/gww, and was secreted into the coronary effluent. Sodium oxamate, an LDH inhibitor, increased ischaemic β-OHB levels 5.3-fold, and slowed contractile recovery. Inhibition of HMG-CoA synthase (HMGCS2) with hymeglusin lowered ischaemic β-OHB accumulation by 40%, despite increased flux through Succinyl-CoA:3-oxaloacid CoA transferase (SCOT), resulting in greater contractile recovery. Hymeglusin also protected cardiac mitochondrial respiratory capacity during ischaemia/reperfusion. In conclusion, net ketone generation occurs in the heart under conditions of low-flow ischaemia. The process is driven by flux through both HMGCS2 and SCOT, and impacts on cardiac functional recovery from ischaemia/reperfusion.