The relationship between domestic dogs and humans represents a unique example of an interspecific relationship. For this and other reasons, there has been a substantial increase in research on dogs. This Special Issue entitled "Dog Behaviour, Physiology and Welfare" collects important information ranging from basic to applied ethology, dealing with canine endocrinology (prolactin, vasopressin, thyroid hormones), physiology (visual perception), welfare (in shelters and zoos), as well as the context of working dogs (service dogs, co-therapist dogs, herding dogs) and the dog-wolf comparison. All the papers are open access and can be read at https://www.mdpi.com/journal/animals/special_issues/Dog_Behavior