This chapter presents the application and use of infrared thermography (IRT) in farm animals and veterinary medicine. Changes in vascular circulation in living organisms result in an increase or decrease in tissue temperature, which is then used to evaluate the situation in the given area. IRT is mainly used in veterinary medicine, primarily for diagnostic purposes, particularly in the diagnosis of orthopaedic diseases in horses. IRT can, however, be used extremely successfully for study and research in farm animals such as pigs, cattle, sheep and poultry. Areas of research include reproduction, thermoregulation, animal welfare and the milking process. Although IRT is applied less frequently in the study of the milking process, recent results show the potential of this measuring method. Generally, IRT is a suitable tool for early detection and screening for mastitis, and can also be useful for studying and evaluating the effects of various milking techniques on the teats and udders. IRT is recommended as a method that can produce important information where the possibilities of conventional diagnostic techniques have been exhausted. There are, however, certain limitations and factors that must be considered when using IRT in animals.