Bartonellae are emerging vector-borne pathogens distributed worldwide that can cause various clinical symptoms in humans and animals, ranging from a mild flu-like illness to more severe manifestations such as endocarditis, myocarditis, arthritis, hepatitis, and arthralgia. Numerous mammalian species, including domestic animals such as dogs, cats, as well as humans, serve as reservoir hosts for various Bartonella species. The vectors play a central role in the transmission of these bacteria and pets and their ectoparasites can pose a serious risk of zoonoses. This paper reviews selected literature on important bartonellosis of dogs, cats, and humans with notes on transmission, vectors, pathogenesis, and diagnosis.