The purpose of this study is to develop a measurement instrument to be used as an assessment tool of teachers’ development of conscientização (i.e., critical consciousness), defined as an individual’s ability “to perceive social, political, and economic contradictions and to take action against the oppressive elements of reality”. After examining the different stages and components of conscientização, the author describes the process of generating initial items, determining the instrument’s format and content validity, and revising the instrument. An exploratory factor analysis (EFA) was conducted with a diverse sample of Teachers of English to Speakers of Other Languages (TESOL), resulting in four internally consistent factors: (a) teacher beliefs about schooling and emotions towards inequality, (b) teacher as activists, (c) teacher awareness of local educational context, and (d) content selection and teaching strategies in the classroom. Psychometric properties of the scale are included.