We report here that a novel 1,869 bp repetitive sequence identified from the false killer whale (Pseudorca crassidens) could be a new molecular phylogenetic marker in cetaceans. Results of PCR amplification and southern blot hybridization using 16 species' genomic DNAs from five different families revealed that the repetitive sequence is highly conserved within all Delphinidae species. Notably, specific primers designed for this repetitive sequence effectively amplified the targeted repetitive units, which were critically dependent upon the genetic phylogenies in the members of the Delphinidae cetaceans. Therefore, the novel sequences can be used as a useful phylogenetic marker for understanding the molecular evolutional studies in members of the Delphinidae family of cetaceans.