This mixed-methods study investigated and compared the professional demotivating factors for EFL teachers in three contexts: high schools, language institutes, and universities. Consequently, a validated questionnaire and semi-structured interviews were employed to gather data from 189 Iranian EFL teachers. The results indicated that the most prominent demotivating factors were financial issues, students' demotivation, facilities and course books, and neglecting teachers for educational decision making. However, financial issues and facilities and course books were less demotivating for university teachers. During the qualitative phase, it was also revealed that supervisors' feedback and attitudes, relationships with colleagues, and preferential treatments negatively affect EFL teachers' motivation. Furthermore, unlike high school teachers, language institutes and university EFL teachers perceive job insecurity as incredibly demotivating.