Teacher attrition is a pervasive issue that affects educational systems globally, contributing to significant challenges in maintaining a stable and experienced teaching workforce. While existing research has explored teacher attrition in various educational contexts, there is a scarcity of studies with in-depth qualitative phases specifically focusing on teacher attrition within language institutes, particularly in English as a Foreign Language (EFL) setting. Therefore, this study employs a mixed-methods approach to explore the factors contributing to attrition among Iranian EFL teachers in language institutes. The qualitative phase involved conducting focus group discussions with five groups of eight Iranian EFL teachers who voluntarily resigned from language institutes and transitioned to freelancing. Additionally, written narrative accounts were collected from each participant to capture their opinions and experiences. Thematic analysis of the qualitative data revealed four main and broad categories of reasons for teacher attrition: financial issues, work environment and support, curriculum and assessment, and challenges in online teaching and learning. In the quantitative phase, a ranking scale was administered to the participants to assess the perceived significance of these identified reasons. Finally, the gathered information was categorized based on the teachers' years of teaching experience. The study's findings shed light on the intricate interplay between individual and contextual factors in EFL teachers' decisions to leave language institutes. These findings have implications for EFL teachers, language institute administrators, and policymakers and provide valuable insights for enhancing working conditions and policies within language institutes.