This handbook brings together contributions from teachers, teacher educators, and school leaders across five Nordic and Baltic countries - Norway, Sweden, Latvia, Lithuania, and Estonia - to examine how research literacy is developed in teacher education and practised in upper-secondary school classrooms. It represents the culmination of the two-year Teacher Research Literacy: Comparative Trajectories in the Nordic-Baltic Region (TREL) project, funded by the Nordplus Horizontal programme.The volume is organised in three parts. The first presents case studies from universities in the participating countries, documenting how research literacy is embedded in pre-service teacher education programmes and how student teachers are supported in moving from research consumers to reflective research practitioners. The second part gives voice to in-service teachers at Norwegian upper-secondary schools who, in partnership with university colleagues, designed and carried out classroom-based action research projects while continuing to teach full-time. These chapters are written in the teachers' own voices and reflect the realities, uncertainties, and professional development that come with integrating research into everyday teaching practice. The third part offers perspectives from school leaders on how to cultivate and sustain teacher research literacy at the institutional level.Taken together, the chapters address two fundamental questions: why teachers need to become research literate, and how teacher education programmes can be designed to support that process. The handbook is intended as a resource for pre-service and in-service teachers, teacher educators, school leaders, and policymakers with an interest in evidence-based teaching and research-informed professional development.