Purpose: Since reflectivity has a crucial role in education, it has attracted researchers' attention in the last decades. As such, the present study aimed to construct and validate a questionnaire to assess the barriers to reflective practices of Iranian ESP (English for Specific Purposes) instructors. Furthermore, this study aimed to investigate the reliability of the scale. Design/methodology/approach: To attain the purpose of the study, the researchers developed the first item pool of the questionnaire which included 67 items. Then, 4 experts were asked to pass their judgments on the items. Accordingly, 37 items were excluded and the next draft of the questionnaire that included 30 items remained. After their feedback, the revised scale was piloted with 10 ESP instructors to check the clarity of items. Then, the scale was administered to 210 ESP instructors. At the next stage, an exploratory factor analysis (EFA) was run to assess the construct validity of the questionnaire. Based on the results, three items were removed. To investigate the internal consistency of the scale, a Cronbach's alpha coefficient was employed. Findings: The final version of the scale included 27 items with three subscales, namely, learners, instructors and institutions' issues. The results revealed that the questionnaire enjoyed an acceptable level of validity and reliability. Originality/value: Apart from a few studies, no other study has scrutinized barriers to EFL teachers' reflectivity. In addition, in the realm of ESP, no study has developed a scale to measure barriers to ESP teachers' reflective practice.