Teachers’ self-regulation (SR), which improves teaching practices, has not received due attention from EFL researchers. This mixed-methods study aimed to examine the SR strategies and teaching effectiveness of English language teachers in Iranian universities and institutes located in three Iranian cities. The first sample of this study comprised 172 EFL teachers (128 males and 44 females) from different socioeconomic backgrounds. Their ages ranged from 23 to 55 years old. The majority of them majored in the different branches of English—English literature (5 BAs, 30 MAs, 10 PhDs), English teaching (10 BAs, 50 MAs,16 PhDs), and English translation (7 BAs, 28 MAs, 16 PhDs). On the other hand, the second sample comprised 153 EFL learners, who were the students of the participating teachers (49 males and 104 females). The age range varied from 14 to 35, and they came from different socioeconomic backgrounds. A study was conducted Teachers completed a Teacher Self-Regulation Scale (TSRS) questionnaire to declare the types and frequency of SR strategies they used while the participating students completed the Characteristic of Successful Iranian EFL Teachers (CSIET) questionnaire, which included ten questionnaire items. According to the quantitative data analysis, SR strategies and teaching effectiveness were negatively correlated. Moreover, 20 EFL teachers were interviewed to determine their awareness of their teaching effectiveness. The study indicates that teachers were not familiar with SR strategies, which can negatively impact their teaching effectiveness. The findings of the study may have insights for teacher educators, administrators, and university teachers, highlighting the role of SR in EFL teaching effectiveness.
