Purpose: While there are established instruments offering psychometrically sound measurement of primary or secondary trauma, none capture the essence of dual exposure for mental health professionals living and working in traumatological environments. Methods: This study examined the experience of 244 mental health workers who lived and worked in New Orleans during Hurricane Katrina. An instrument, the Shared Trauma and Professional Posttraumatic Growth Inventory (STPPG), a 14-item, Likert-type scale composed of three subscales (Technique-Specific Shared Trauma, Personal Trauma, and Professional Posttraumatic Growth), was developed to understand the nature of dual trauma exposure. Results: The STPPG supports the reciprocal nature of shared trauma and correlates well to existing measures for posttraumatic stress, secondary trauma, shared trauma, and posttraumatic growth. Discussion: The STPPG suggests that personal traumatic experience can impact professional practice, and client traumatic narratives influence one's personal trauma responses. Implications of STPPG for practice and future research are discussed.