A dead-stranded adult male Atlantic white-sided dolphin was found in March 2005 on the Sand Voe, Mainland, Shetland, UK. Postmortem examination was performed and samples of the lung, liver, spleen, kidney, forebrain, meninges adherent to the atlanto-occipital joint, mesenteric lymph node, blood and small intestines were collected for histopathological examination and bacterial isolation. Gross postmortem examination revealed the presence of bloodstained fluid and froth in the trachea, oedematous and congested lungs and congested liver. Histopathological examination of the brain showed mild autolysis and a generalized non-suppurative meningoencephalitis. A focal non-suppurative choroiditis was also present, and there were small amounts of meningeal serum leakage. A profuse growth of Brucella species was recovered from the meninges adherent to the atlanto-occipital joint, together with a scant growth from the brain, and a single colony was recovered from the kidney. To the authors' knowledge, this is the first reported case of Brucella species bacteria being isolated from a diseased synovial joint of a cetacean.