Veterinary microbiology is a branch of microbiology (study of unicellular, multicellular and acellular microscopic organisms) that deals with the role of microbes in veterinary medicine or animal taxonomy. Basically, it covers the microbial agents which affect animals. It is the study of the variety of disease-causing microorganisms which include bacteria, viruses and parasites. Veterinary microbiologists are veterinarians who specialize in the study of microorganisms which cause disease in animals. Their duties may vary depending on their specific area of study, but basically their work include the administration of advanced laboratory analysis using microscopes and similar devices, examination of animal tissues and fluids, as well as providing consultations to general practitioners upon request.

Veterinary microbiology focuses on several areas of microbiology, such as immunology, bacteriology, virology, mycology an parasitology. Practitioners may either focus their study on a particular species of animal, or a diverse group of animals. Their research covers both endemic and exotic animal diseases, biological and pathogenic properties of organisms, their role in health and disease of animals and the resposnse of the host to infection. Moreover, veterinary microbiology focuses on the treatment of infectious diseases.

Veterinary microbiology also deals the ecologic associations within the animal kingdom: parasitism, mutualism and commensalism. Parasitism is a non-mutual relationship between organisms where one organism, called the parasite, benefits from the relationship at the expense of the other organism, called the host. Parasites are permanently associated with their animal hosts, growing, feeding and finding shelter while contributing nothing to the latter's survival, rather reducing the hosts' biological fitness.

Commensalism is a type of relationship between two organisms wherein one benefits without really affecting the other. Like all of the ecological interactions in nature, commensalims may differ in strength and duration: some have long-lived symbioses while others have weak interactions through intermediaries in a shorter period of time. Mutualism is a relationship wherein two organisms belonging to different species exist in an interaction in which each of them benefits. It is a type of symbiosis which plays a vital role in ecology itself. Mutualistic transversals can be considered as a kind of 'biological barter' wherein species trade resources or services.