The present study was conducted to examine the relationship between the self-supervision and the self-efficacy of Iranian EFL teachers and also the relationship between the self-supervision and the self-efficacy of intermediate adult learners individually. To this end, 40 EFL teachers and 55 intermediate adult learners were selected from two branches of Kish Language Institute. In this study, “Self-Supervision checklists” were formed separately for the teachers and the learners to collect data. Common European Framework (CEF) and that of the Association of Language Testers in Europe (ALTE), the two internationally standard scales were used as learners’ checklists. Besides, an independent t-test was run to determine the statistical difference between the means on two sets of scores: the teachers’ self-supervision and the institutional supervision; the learners’ self-supervision and the institutional assessment. Data analysis and statistical calculations revealed a positive relationship between the teachers’ self-supervision and their self-efficacy in language teaching, and it also showed a positive relationship between the learners’ self-supervision and their self-efficacy in their language learning.