Older pregnant women have increased risks of complications including gestational diabetes and stillbirth. Carnitine palmitoyl transferase (CPT) expression declines with age in several tissues and is linked with poorer metabolic health. Mitochondrial CPTs catalyze acylcarnitine synthesis, which facilitates fatty acid oxidization as fuel. We hypothesized that the placenta, containing maternally-inherited mitochondria, shows an age-related CPT decline that lowers placental acylcarnitine synthesis, increasing vulnerability to pregnancy complications. We assessedCPT1A,CPT1B,CPT1CandCPT2mRNA expression by qPCR in 77 placentas and quantified 10 medium and long-chain acylcarnitines by LC-MS/MS in a subset of 50 placentas. Older maternal age associated with lower expression of placentalCPT1B, but notCPT1A,CPT1CorCPT2.CPT1Bexpression positively associated with eight acylcarnitines andCPT1Cwith three acylcarnitines,CPT1Anegatively associated with nine acylcarnitines, whileCPT2did not associate with any acylcarnitine. Older maternal age associated with reductions in five acylcarnitines, only in those with BMI≥ 25 kg/m2, and not after adjusting forCPT1Bexpression. Our findings suggest thatCPT1Bis the main transferase for placental long-chain acylcarnitine synthesis, and age-relatedCPT1Bdecline may underlie decreased placental metabolic flexibility, potentially contributing to pregnancy complications in older women, particularly if they are overweight.