Dog (Canis familiaris) has been the first species to be domesticated by humans. This was the result of an interactive process that took place throughout thousands of years and led to competence, cooperation and coevolution relationships. Through a convergent evolution process, dogs have been able to acquire social abilities, similar to those of humans, which enabled particular communication ways between the two species. Dogs' remarkable ability to understand human social and communicative behaviors (even better than genetically related species, such as primates) favored their relationship with humans. Although some debate arose about the accuracy of the concept attachment, evidence of the most recent investigations on behavioral and endocrine responses in human-dog interactions have supported the idea that this relationship represents an expression of attachment. The oxytocin role has stood out in the formation of attachment bonds and in prosocial behavior that encourages intraspecies relationships. It achieves this by inducing maternal behaviors in a persistent fashion, influencing on pairing and increasing interpersonal trust through eye contact, empathy, etc. Moreover, the participation of oxytocin in the social bond processes is complex, as it has shown to play multiple roles. Oxytocin influences on the stress by reducing the cortisol levels, modulates the amygdala activity linked to fear, and increases the pain threshold, among other actions. Research in the human-animal interaction field, or Anthrozoology, has highlighted the companion animals' contribution to people wellbeing and particularly the buffering effect on daily life stress. The idea that living with an animal can have a positive influence on human health has been called pet effect and has been studied understanding physiological, psychosocial and therapeutic aspects. We carried out a systematic bibliographic review of the empiric studies about human-dog interactions in which oxytocin levels were assessed or oxytocin was administered, in dogs and / or humans. We present the employed procedures and the main results, and analyze the limitations and relevance of the investigations' findings, as well as their consistencies and contradictions. The results are discussed in function of the findings related to oxytocin and its intraspecies effects, and also in function of the development in Anthrozoology in general. The possible role of the oxytocin in the different aspects of the human-dog relationship is analyzed. Among these aspects we highlight the pet effect, and the reported benefits of the relationship human-companion dog, mainly related to a decrease in stress symptoms; anthropomorphism and the mental states attribution necessary so that pet keeping makes sense; and the cute response, which implies an instinctive reaction to give parental care as a response to the infantile scheme, thought to be involved in the origin of pet keeping. The oxytocin role as an underlying neuroendocrine substrate that explains the benefits of the positive social experience that implies the human-dog bond and promotes the strengthening of this reciprocate and shared bond is emphasized. Finally, new lines of investigation are considered, such as the empiric study of the relationship of this neurohormone with the anthropomorphism and the response to the infantile scheme. We lay stress on the importance of developing studies with samples that include humans and dogs of different ages, with the object of assessing the influence of age on the response to oxytocin. We also make a point of the relevance of carrying out comparisons in relation to the human and dog gender, which has been usually controlled rather that investigated. Furthermore, we discuss the validity of the techniques employed to measure and administer the oxytocin. We make recommendations about these techniques and their use for considering the investigations goals. We highlight the least invasive methods such as the urine oxytocin measure, which are related to a more spontaneous behaviors and are more in agreement with animal welfare.