Aims: The sympathetic nervous system regulates numerous aspects of mitochondrial function in the heart through activation of adrenergic receptors (ARs) on cardiomyocytes. Mounting evidence suggests that α1-ARs, particularly the α1A subtype, are cardioprotective and may mitigate the deleterious effects of chronic β-AR activation by shared endogenous ligands. The mechanisms through which α1A-ARs exert their cardioprotective effects remain unclear. Here we tested the hypothesis that α1A-ARs adaptively regulate cardiomyocyte oxidative metabolism in the uninjured and infarcted heart. Methods: We used an α1A-AR knockout mouse (α1A-KO) to characterize the effects of α1A-AR genetic deletion on mitochondrial function and metabolism in the uninjured mouse heart using high resolution respirometry, substrate-specific electron transport chain (ETC) enzyme assays, transmission electron microscopy (TEM) and proteomics. We then compared the effects of α1A- and β-AR agonist treatment on mitochondrial function in uninjured mice and mice subjected to experimental myocardial infarction. Results: We found that isolated cardiac mitochondria from α1A-KO mice had deficits in fatty acid-dependent respiration and ETC enzyme activity. TEM revealed abnormalities of mitochondrial morphology characteristic of these functional deficits. The selective α1A-AR agonist A61603 enhanced oxidative metabolism in isolated cardiac mitochondria. The β-AR agonist isoproterenol enhanced oxidative stress in vitro and this adverse effect was mitigated by A61603. A61603 enhanced ETC Complex I activity and protected contractile function following myocardial infarction. Conclusions: Collectively, these novel findings position α1A-ARs as critical regulators of cardiomyocyte metabolism in the basal state and suggest that metabolic mechanisms may underlie the protective effects of α1A-AR activation in the failing heart.