The purpose of this study was to develop an instrument to measure K-12 teacher demoralization. An increasing body of literature has labeled modern education policies as having a demoralizing effect on teachers (Darling-Hammond & Rustique-Forrester, 2002; Noddings, 2004; Ryan & Brown, 2005; Nichols & Berliner, 2007; Santoro, 2011; Hargreaves, Braun, & Gebhardt, 2013). Teacher demoralization has been defined as a teacher’s “inability to access the moral rewards of teaching” (Santoro, 2011, p. 3). Data was collected from a population of K-12 educators through cognitive interviews (n=6) and a large scale data collection analyzed with a principal component analysis (n=430) in an effort to determine which constructs should be included in the measurement of teacher demoralization. Feedback on the survey instrument was incorporated in an iterative process at each stage of data collection. Results revealed that the theory of teacher demoralization should include two factors: teacher dispositions and feelings of demoralization. The current study failed to find strong evidence of convergent validity with teacher burnout and self-determination need thwarting; however, results suggest that emotional exhaustion and autonomy need thwarting are moderately related to teacher demoralization. Evidence of discriminant validity in relation to teacher self-efficacy was found; however, other discriminant validity evidence was inconclusive. This study extends the literature by providing the first attempt to measure the phenomenon of teacher demoralization. Future studies should continue to refine the instrument of teacher demoralization, and can use this instrument as one way to examine the impact of policy on teachers.