Secondary traumatic stress (STS) is an increasingly recognized mental health concern among professionals working with trauma survivors. Although STS shares symptomatic overlap with post-traumatic stress disorder (PTSD), its etiology is rooted not in direct trauma exposure but in empathic engagement with traumatized individuals in the course of professional responsibilities. This crucial conceptual distinction is often neglected in both the mental health literature and clinical settings. This narrative review explores the theoretical underpinnings, diagnostic challenges, and psychosocial consequences of STS, with a particular focus on professionals operating in disaster zones.