Perinatal heart maturation is associated with a switch in energy substrate preference from glucose metabolism to fatty acid (FA) oxidation. The cause of this metabolic switch is unknown. The late gestational surge in glucocorticoids (GC) is critical for the structural and functional maturation of the fetal heart and may contribute to metabolic maturation. Here, we hypothesized that GC promote a switch to fatty acid oxidation in late gestation fetal cardiomyocytes. Primary mouse fetal cardiomyocytes were cultured following collagenase and pancreatin digestion of embryonic day (E)14.5-15.5 hearts. Two days later, cells were treated with RU486 (GR antagonist) or vehicle for 30 minutes prior to 24h treatment with 1mM dexamethasone. Mitochondrial respiration and glycolysis were measured using a Seahorse XF24 Analyzer. Respiration was measured in the presence of the FA, palmitate (100mM) and the mitochondrial FA uptake blocker etomoxir (6mM) or vehicle. Mitophagy was assessed following dexamethasone treatment of cultures of fetal cardiomyocytes from MitoQC mice in which an increase in red puncta is indicative of mitophagy. Mitochondrial volume was measured using MitoGraph software following staining with Mito-tracker deep red FM or using MitoQC cardiomyocytes. Dexamethasone did not alter glycolysis. In the presence of palmitate, dexamethasone increased basal respiration and ATP production. This was attenuated by etomoxir or RU486. Neither mitochondrial volume or mitophagy were affected by dexamethasone. Consistent with an increase in FA oxidation, dexamethasone increased the expression of genes involved in FA uptake (Cd36, Cpt1a, Cpt1b) and utilization (Lcad, Mcad, Lipin1, Ppargc1a) but not Sirt1 (involved in autophagy and metabolism) and Scad (short chain FA utilization). These data support a glucocorticoid-induced switch in substrate preference towards FA oxidation in fetal cardiomyocytes through changes in gene expression rather than gross changes in mitochondrial volume or inducing mitochondrial turnover.