<p>While negative emotions signal developmental potential, the mechanisms through which language teachers transform cognitive-emotional dissonance into actual learning remain insufficiently understood. Grounded in the Complex Dynamic Systems Theory (CDST), specifically the concept of perturbation, this study explores how two secondary school EFL teachers negotiated dissonance during a year-long action research (AR) project within a school-university partnership. Qualitative data were collected from semi-structured interviews, observations, reflective journals, and research artifacts. Findings reveal that the conflicting beliefs, knowledge gaps and epistemological differences between practitioners and researchers functioned as perturbations that destabilized the teachers’ initial equilibrium and triggered transformative learning. Their disparate and non-linear trajectories emerged from adaptive interactions between internal teacher systems and nested contextual sub-systems, including the program, the classroom, and the research community. This study underscores CDST’s utility in capturing the fluid and emergent nature of teacher learning. It suggests a need for teachers to develop robustness and open-mindedness to embrace disruptive experiences like AR and for teacher educators to construct resourceful and responsive systems to foster teacher development.</p>