Service canine companionship and oxytocin (OT) appear to be on parallel tracks as novel candidate PTSD treatments or treatment enhancers. A wealth of anecdotal evidence has emerged from U.S. military clinical settings supporting the benefits of service canine companionship and canine-assisted interventions for military personnel with deployment-related mental health conditions; however, rigorously empirical support for this approach remains sparse. A growing literature exploring the role(s) of the OT system in PTSD now includes a number of encouraging findings. For example, in PTSD, OT modulates amygdala hemodynamic responses to emotional faces and increases anterior insula hemodynamic responses to social rewards. Intranasal OT administration normalizes amygdala functional connectivity in PTSD and increased subjective compassion for other persons. These findings align with findings in healthy persons. After intranasal administration, normal adults gaze more at the eye region of faces, have better memory for faces, are better able to infer the mental states of others, have more positive communications, are more generous, rate faces as more trustworthy owe, and exhibit increased trust behavior. OT also attenuates startle in healthy persons, attenuates amygdala responses to fear-inducing stimuli, and inhibits the stress-responsive release of cortisol. In turn, the human findings generally agree with a large animal literature showing that OT plays an important role in social behaviors such as partner preference, social bonding, and social cognition, while OT dysregulation produces a variety of social impairments.