Canine thyroglobulin (cTg) is one of the thyroid autoantigens associated with hypothyroidism caused by autoimmune thyroiditis in dog. To identify canine-specific areas in cTg, we cloned, by reverse transcriptase PCR, and sequenced the complete cDNA of cTg. It revealed an open reading frame of 8289 nucleotides, which encode a polypeptide of 2762 amino acids that is 78.9 and 78.1% identical to bovine and human thyroglobulin, respectively. This complete cTg sequence may be useful to promote the understanding of the primary structure of cTg and, it will be informative data in the further search about antigenic epitopes associated with autoimmune thyroiditis and pathogenesis of cTg-associated thyroid diseases in dog.