Brucellosis is reported increasingly in marine mammals and the marine species of Brucella are capable of causing community acquired zoonotic infections in humans as well as abortion in cattle as a result of experimental infection. This case report describes pathology associated with an isolate of Brucella ceti that was successfully cultured from, and immunolabelled in, the testis and epididymis of an adult sexually mature free-living harbour porpoise (Phocoena phocoena). This is the first report of such pathology in any species of cetacean, and suggests the potential for sexual transmission and/or sterility as sequelae to infection similar to those reported in terrestrial animals.