The main purpose of the present study was to systematically scrutinise the possible relationship between English as a foreign language (henceforth EFL) teachers' professional and institutional identity with their teaching efficacy. In doing so, 100 EFL teachers and instructors, within the age range of 30 to 50 (mean age = 40), and teaching experience of 5 to 25 years, teaching at private language institutes and public schools in Hamedan were selected based on convenience sampling strategy. They were asked to fill in three questionnaires, namely, the Liou's "Professional Identity Questionnaire" (2008), the Azimi's "Institutional Identity Questionnaire" (2012), and the Tschannen-Moran, Hoy and Hoy's "Teachers Efficacy Scale" (1998). To test the research hypotheses of the study, two separate Pearson product-moment coefficients, and a multiple-regression were applied. The findings of the study showed a statistically significant positive association between EFL teachers' professional identity and their teaching efficacy. Furthermore, the findings also indicated that there was a significant positive association between EFL teachers' institutional identity and their teaching efficacy. Additionally, it was found that professional identity was a better predictor of EFL teachers' teaching efficacy. Considering the findings of the study, teacher trainers and administrators are thus recommended to organise some preparation conferences and hold different workshops in order to familiarise EFL teachers with both practical and theoretical bases of teachers' identity, and also improve their actual teaching efficacy