Emotional support animals (ESAs) are different from service animals, therapy animals, and other disability-related assistance animals. Although pet ownership may confer psychological benefits, limited research has supported the use of ESAs to realize such benefits. If clinicians are asked to write a letter of support for use of an ESA, they need to be familiar with relevant federal, state, and local laws that regulate ESAs and with the essential components of an ESA evaluation. This article provides an overview of terminology; federal, state, and local laws related to ESAs; and clinical and ethical considerations for clinicians who decide to write these letters. The authors also review liability issues related to writing these letters, including those related to ESA aggression.