There is a substantial body of studies investigating teachers' beliefs about pronunciation. However, this line of research has rarely examined teachers' beliefs as a complex system. To fill this gap, the present study aims to shed light on the genealogy of teachers' beliefs about pronunciation instruction from the perspective of complexity theory. To this end, two EFL teachers who taught English at a private institute were asked to participate in this study. Data were collected using semi-structured interviews and narratives. The findings indicated that the teachers recognized the importance of pronunciation instruction for improving students' listening skills and knowledge of vocabulary and manifested aspiration for native-like pronunciation. However, their lack of self-confidence and insufficient pronunciation pedagogical knowledge base were reported to be major challenges of pronunciation instruction, which they attributed to teacher training courses among other factors. In addition, teachers' beliefs about pronunciation, learners, learning pronunciation, teaching pronunciation, teachers, and curriculum were shown to co-exist and interact in a nonlinear manner, suggesting the complex, dynamic, co-adapted, and contextual-driven nature of teachers' belief systems. In light of these findings, teacher education programs are advised to help teachers reappraise their preference for native speakerism and give pronunciation more prominence by introducing a wide range of strategies for teaching it.