Augmented reality (AR) refers to the introduction of virtual elements in the real world. That is, the person is seeing an image composed of a visualization of the real world, and a series of virtual elements that, at that same moment, are super-imposed on the real world. The most important aspect of AR is that the virtual elements supply to the person relevant and useful information that is not contained in the real world. AR has notable potential, and has already been used in diverse fields, such as medicine, the army, coaching, engineering, design, and robotics. Until now, AR has never been used in the scope of psychological treatment. Nevertheless, AR presents various advantages. Just like in the classical systems of virtual reality, it is possible to have total control over the virtual elements that are super-imposed on the real world, and how one interacts with those elements. AR could involve additional advantages; on one side it could be less expensive since it also uses the real world (this does not need to be modeled), and it could facilitate the feeling of presence (the sensation of being there), and reality judgment (the fact of judging the experience as real) of the person since the environment he or she is in, and what he or she is seeing is, in fact the "reality." In this paper, we present the data of the first case study in which AR has been used for the treatment of a specific phobia, cockroaches phobia. It addresses a system of AR that permits exposure to virtual cockroaches super-imposed on the real world. In order to carry out the exposure, the guidelines of Ost with respect to "one-session treatment" were followed. The results are promising. The participant demonstrated notable fear and avoidance in the behavioral avoidance test before the treatment, and not only was an important decrease in the scores of fear and avoidance observed after the treatment, but also the participant was capable of approaching, interacting, and killing live cockroaches immediately following the treatment. The results are maintained in a follow-up conducted 1 month after the termination of the treatment.