Aromatic l-amino acid decarboxylase (AADC) enzymatic activity is essential for the biosynthesis of the serotonin and dopamine neurotransmitters, and AADC activity is functionally associated with a number of human neuronal disorders. Here we describe the molecular characterization of AADC from the pig. Pig AADC shows a high degree of similarity to human and rodent AADC at the cDNA and protein level. Exon position shuffling has exchanged the location of the stop codon in pig AADC to the last exon 15 instead for the exon 14 position in the human, the rat, and the mouse AADC. Several pig AADC isoforms were identified, including the also in human described extraneuronal and neuronal isoforms generated by alternative splicing and alternative promoter usage. The AADC expression in the developing pig brain is highly expressed in the basal ganglia and the brain stem regions, and also significantly expressed in the cortex, the hippocampus and the cerebellum. Moreover, we observe that both the neuronal and the extraneuronal AADC mRNA isoforms were present at early brain developmental stages in the brain stem and the basal ganglia. This presents the first evidence that the non-neuronal AADC isoform also is expressed in the brain. Together our results propose that the porcine model is useful for future functional delineations of the AADC gene at the molecular level.