The transformational approach (Freire, 1998) can be achieved through critical pedagogy. The present study describes the development and validation of a questionnaire to access critical pedagogy for evaluating teachers’ perceptions of critical pedagogy in two different contexts i.e. public and private schools. This study used a mixed-method design. In the qualitative phase, 15 experienced high school teachers from public and private schools in Sabzevar, Iran, participated in a semi-structured interview. Based on the result of the constructivist grounded work and the literature review, the main constructs of critical pedagogy were described. Then, an eight-construct operationalization of language teaching was presented, describing the fundamental principles of language teaching from the point of view of critical pedagogy. In the quantitative phase, 180 valid questionnaires, obtained from 59 males and 121 females, were used to run the Confirmatory Factor Analysis using the software LISREL 8.5. This resulted in a 70-item, five-point Likert-scale instrument with satisfactory construct validity which was based on the 21 constructs of critical pedagogy. As a validated measurement, the Critical Pedagogy Questionnaire can be highly useful for the researchers and designers in the field of ELT, English teachers, and instructors to evaluate the perception of their learners on critical pedagogy.