Therapeutic presence brings one’s whole self into the encounter with clients by being completely in the moment on multiple levels: physically, emotionally, cognitively, and spiritually. Drawing from polyvagal theory, this paper present a bio-behavioral explanation of how therapeutic presence can facilitate a sense of safety in both play therapist and client, to deepen the therapeutic relationship and promote effective therapy. According to the theory, when safety is communicated via expressed markers of social engagement (e, g., facial expressions, gestures, and prosodic vocalizations), defensiveness is down-regulated. Cultivating presence and engagement in present-centered relationships can therefore facilitate effective therapy by having both client and play therapist enter a physiological state that supports feelings of safety, positive therapeutic relationships, and optimal conditions for growth and change.