The low production of hypotaurine from cysteine but a significantly high taurine deposition in common carp led to the hypothesis that this species utilizes an alternative pathway other than the cysteine sulfinic acid pathway. Cysteamine pathway is common in mammals but not in other animals such as birds, invertebrates, and fishes. The cloned cysteamine dioxygenase (ADO) cDNA in common carp consists of 790 nucleotide bases with 260 deduced amino acid sequence. The conserved domain is the DUF1637 which has a conserved tyrosine and cysteine residues and the presence of three predicted N-glycosylation sites. Phylogenetic analysis using neighbor joint method indicated that ADO in common carp branched after Sinocyclocheilus rhinocerous. ADO was expressed in hepatopancreas, brain, gill, intestine, and muscle of common carp. The hepatopacreas had a significantly higher gene expression level than the other organs examined. The present results suggest that ADO is present in common carp.