The targeted student profile in the changing world is now aimed at being an individual who plays an active role in their learning process, investigates, questions, thinks and discovers rather than a passive recipient who acquires the information that the teacher understands. Such a student profile requires an understanding of teaching that aims to be equipped with a variety of competencies, rather than the transfer of information that can be acquired in a very short period of time from many sources. Being able to adapt to the ever-evolving and changing dynamics of 21st century, in order to train students equipped with century skills, it is inevitable that teachers will be constantly engaged in reflective thinking practices and guide their own development. This study aims to examine the reflective thinking processes of teachers in a school that is involved in the International Baccalaureate (IB) Middle Years Program (MYP) process adopted and implemented by many schools in Turkey, to reveal how they perceive change in this process and to examine the action plans they develop in the process of change. The study was carried out with 16 participants from different branches. Teachers from branches of Physical Education, Mathematics, Social Studies, Science, Turkish, English Teaching, Technology-Design, Music, Visual Arts, working at IB MYP School were participated in the study. In the study, a semi-structured interview form was used as a data collection tool. Descriptive analysis was used. It is seen that teachers' perceptions of change are clustered within certain frameworks, independent of the branch. The main ones are teaching approach, professional development practices, curriculum, philosophy, planning, collaboration, teaching process.