This paper reports the study undertaken on types of defense mechanisms used by Iranian EFL teachers. Furthermore, the significant differences between male and female EFL teachers at different age groups in the use of defense mechanisms are also considered. In the first phase of the study, the focus was on identification of defense mechanisms teachers generally adopt in their daily activities, while the second phase was exclusive to the deployment of defense mechanisms inside EFL classes. Accordingly, Defense Style Questionnaire was distributed among 100 EFL teachers. Next, to capture in-class atmosphere, the researchers carried out 30 semi-structured interviews with Iranian EFL teachers. All the participants (15 males and 15 females) were teaching in public schools as well as private institutes at the time of the interview. The results of the questionnaire indicated that teachers used two mature defense mechanisms, namely, anticipation (M=13.8) and rationalization (M=13), in their daily lives more than the others. Nonetheless, the results of the interview denoted the dominance of pseudo- altruistic behaviors (N=30), as a neurotic mechanism, in EFL classes. Sublimation and humor (N=29), as two mature defense mechanisms, were also frequently used. On the other hand, splitting (N=2), passive aggression (N=2), and projection (N=3), all of which are considered to be immature mechanisms, were the least-frequently used mechanisms. Moreover, Mann-Whitney and Kruskal-Wallis tests signified no significant differences in terms of gender and age in the use of defense mechanisms among Iranian EFL teachers.