This disclosure relates to mRNA therapy for the treatment of maple syrup urine disease (MSUD). mRNAs for use in the invention, when administered in vivo, encode branched chain α-ketoacid dehydrogenase complex (BCKDC) E1α, E1β, or E2mRNA therapies of the disclosure increase and/or restore deficient levels of E1α, E1β, or E2 expression and/or BCKDC activity in subjects. mRNA therapies of the invention further decrease abnormal accumulation of branched chain amino acids associated with deficient BCKDC activity in subjects.