Teacher agency is a concept that defines a teacher's commitments and capabilities of making decisions and taking actions which result in a change in the community of teaching (Husu & Toom, 2010; Pietarinen, Pyhälto & Soini, 2016). Since practicum teaching is the first place where teacher trainees enhance both theoretical and practical teaching experiences, it plays a crucial role in shaping teacher trainees' professional agency. Putting emphasis on the practicum teaching and different instructional backgrounds, this study aims to describe English language teacher trainees' sense of professional agency in practicum in Poland, Portugal, and Turkey. In addition, it attempts to compare three practicum settings in terms of the professional agency. The main findings of the study show that teacher trainees have a sense of professional agency in three countries but their level of agency varies. Considering the dynamics of agency, it can be stated that teacher trainees feel more agentic in reflection. Turkish and Portuguese practicum contexts show similarities in the components of reflection and positive interdependence; however, three countries significantly differ in the sense of professional agency from a holistic perspective.