Obesity is a major issue in veterinary medicine. It is not only an accumulation of fat, but obesity also has important cardiovascular and respiratory implications. Therefore, it can strongly influence the anesthesia in obese patients. In addition, obesity can have an underlying cause or may lead to related conditions, which can complicate the anesthesia. Finally, obesity leads to changes in the pharmacodynamics and kinetics of certain drugs, such as anesthetics. These changes require dose adjustments depending on the anesthetic. Unfortunately, the available information is very limited in veterinary medicine and is mainly obtained by extrapolation from human medicine. In this article, an overview is provided of the pathophysiological and pharmacological changes in obese animals, which are important during anesthesia.