Background: Complex Organizational Trauma (COT) is a prolonged state of organizational dysfunction and chaos marked by ineffective responses and the inability to effectively manage agency operations. COT occurs as a reaction to multiple incidents of sustained organizational trauma and is characterized by multiple crises that erode an organization’s capacity to accomplish its mission. COT is conceptualized across three levels: (1) individual trauma history of employees and supervisors, (2) quality of work environment, and (3) sudden policy change and financial uncertainty. Together, these three factors may trigger COT, resulting in dysfunctional operating practices, reduced resources, and lack of viability. Objective: The absence of a reliable assessment tool hinders organizations from responding to COT. The object of this study is to develop a measurement tool, the Complex Organizational Trauma 21 Item Scale (COT-21), to measure COT. Method: The Latent Variable Model Framework was used to develop the scale. Four organizations participated in the study (n=167). Descriptive statistics were performed on the COT-21 survey results. To gather psychometric properties, Exploratory Factor Analysis (EFA) and Cronbach’s Alpha were used. Results: The results show positive support for the COT-21 scale. The coefficient alpha for the COT-21 total scale is considered good (α = .81), indicating good internal consistency. Utilizing EFA, items were grouped into four subscales, suggesting good validity. Discussion: This study advances social work research by presenting results that validate the COT-21 Scale. The implications for use of the COT-21 in a variety of assessment contexts are discussed.