Instruments currently utilized in research on secondary traumatic stress (STS) fail to measure distress and impairment. To fill this gap, this article describes the development and initial validation of a new instrument designed to measure distress and impaired functioning related to work-related secondary trauma exposure. The Secondary Trauma Impact Scale (STIS) is a brief screening measure consisting of six items, each measuring a different domain of distress and impairment. Domains include social, occupational, familial, sexual, psychological, and physical functioning. Secondary analysis was conducted on data collected from 577 master's-level social workers for a previously reported study. Results strongly support the reliability and factorial, convergent, and discriminant validity of the STIS. The ability to explicitly measure secondary trauma-related distress and impairment with a reliable and valid instrument will allow social workers to obtain more precise estimates of the prevalence of STS, identification of risk and resilience factors, and evaluation of interventions targeting the impact of STS on individuals and organizations.