This study aimed to pre-service teachers' reflective thinking and to reveal development of reflective thinking during the process of teaching and learning. This study was designed in the form of action research due to the nature of the case examined. The participants were 4 pre-service teachers at Bayburt University Faculty of Education Department of Elementary Science Education. Video recordings and reflective journals were used to collect the data for study. The qualitative data obtained were analyzed using the content analysis method. Reflective thinking skills developed at the end of the training process of pre-service teachers. However, the work of reflective thinking, planning a course for pre-service teachers participating in this study was shown to contribute to the professional development for the implementation and evaluation. The work done to improve the process of reflective thinking of pre-service teachers is determined to have a level reflecting the start of the technical field. At later stages of the process pre-service teachers are determined level of application and critical reflection levels. In this context, experience of pre-service teachers and reflection on these experiences provide that reflective thinking skills development for the planning, implementation and evaluation of a lesson.