Improving teaching and assessment practice requires a change in the attitudes of both teachers and learners towards the new trends introduced in the field of testing. The reason for this is that no educational change can be effectively and efficiently implemented unless teachers are not only convinced but also willing to implement the new achievements. The present study aims to investigate one aspect of teacher attitudes toward self-assessment in which learners take the responsibility of assessing their own language performance. A qualitative research was launched by using an attitude questionnaire. Thirty-two staff members and part time language teachers from different departments of the Faculty of Foreign Languages and Literatures took part in this study and answered the questionnaire. The results of this study confirmed the directional hypothesis assumed by the researcher that Iranian language teachers at the University of Tehran hold a negative attitude towards alternative assessment in general and self-assessment in particular. It was observed that years of experience also created a kind of fixation on the traditional methods of teaching as well as assessment these teachers used in their classes. It was also shown that unfamiliarity with the new trends in language assessment was generally shared by experienced ones while the novice teachers enjoyed the advantage of familiarity with them. This familiarity did not eventually lead to the use of the new methods due to the existence of several factors. The main one is the resistance these teachers usually hold about change in general. Another reason for the teachers’ negative attitude towards the use of self-assessment can be that teachers believe that by using self-assessment they are relinquishing the power and authority in class to the learners.