Listeria monocytogenes can cause disease and death in humans and a large variety of animal species.Canine listeriosis seems, however, to be rare. In the present report, L. monocytogenes was isolated as apure culture from the gallbladder of a dog with liver insufficiency. The animal suffered from auto-immune-mediated polyarthritis and had therefore been treated with prednisolone for several months. The L.monocytogenes isolate tested positive in PCR for the virulence genes inlA, inlB, hly, actA, sigB and prfA andexpressed functional, full-length internalin. This is the first reported case of a dog with a L. monocytogenesinfection of the gallbladder. Bacterial persistence in the gallbladder of pet animals may constitute a healthhazard for their owner.