Helicobacter spp. occur in the digestive system of a broad range of animal taxa, including marine mammals. Only one formally recognized species, Helicobacter cetorum, has been described in marine mammals. Here we report a novel Helicobacter with the proposed name Helicobacter sud-cetorum (strain ID: ATFT1), was cultured from the main stomach of a wild, stranded spotted dolphins (Stenella attenuata). The dolphin species was confirmed by nucleotide sequencing of mitochondrial t-RNA. The young dolphin (< 2 years old) was found stranded in Port Beach, Western Australia, Australia and deceased in the Perth Zoo. Preliminary autopsy reported that the dolphin’s body was in poor condition due to malnutrition and “ulcers” were observed in both the main and pylorus stomachs. However, histology examination suggest otherwise as there was no sign of inflammation in the biopsies collected even though moderate amount of spiral organism was observed. Multiple isolates were able to be cultured from various location of the main and pylorus stomachs under microaerobic conditions at 37°C and all tested positive for catalase, oxidase and urease. Antimicrobial sensitivity testing revealed that it is sensitive to amoxicillin, metronidazole, clarithromycin, ciprofloxacin, rifampicin, tetracycline and furazolidone. Nucleotide sequence of partial 16s rRNA suggested that it is most closely related to the H. cetorum, in particular strain M74, which was isolated from a different dolphin species (Delphinus delphis) in Southwest coast of England.Electron microscope showed its spiral morphology with multiple flagellum (n>10) present at single polar. Lipopolysaccharide (LPS) staining revealed the absence of all the heavy O-antigen that present in H. pylori. This study showed that (i) H. sud-cetorum (ATFT1) may not be immunogenic; (ii) dolphin, similar to human, can be infected at young age and (iii)H. sud-cetorum can be spread between different dolphin species host.