Maple syrup urine disease (MSUD), also known as branched-chain alpha ketoaciduria, is a metabolic disorder caused by an inborn deficiency in the activity of the branched-chain alpha-ketoacid dehydrogenase complex. Severe neurological damage occurs in most patients with MSUD although the exact mechanism of neurotoxicity still remains unknown. Studies have suggested that neuropathology in patients with MSUD may be related to oxidative stress. L-carnitine mediates the transport of fatty acids into the mitochondria that are required for beta-oxidation and ATP production. Along with the important roles it plays in lipid metabolism, L-carnitine also protects tissues from oxidative damage through its antioxidant properties. The study included a total of 15 patients with MSUD who attended regular follow-up visits, and 15 age-matched healthy control subjects, and aimed to investigate L-carnitine levels in treated patients with MSUD and healthy control subjects. L-carnitine levels were found to be significantly lower in the patient group than in the healthy controls. No significant correlation was identified between the plasma branched-chain amino acids leucine, isoleucine, valine, and L-carnitine levels. Patients with MSUD can be treated with adjuvant therapy with L-carnitine supplementation.