The aim of this study is to examine the effect of the learning environment designed based on different approaches on the change in pre-service teachers' approach preferences and geometry achievement in geometry problems. Twenty pre-service mathematics teachers were involved in geometry lessons for 10 weeks in a learning environment designed based on Analytic Approach (AA), Synthetic Approach (SA) and Vectorial Approach (VA). There were six geometry problems in the pre-test and post-test administered before and after the implementation, respectively. The solutions of the problems in these tests were evaluated by means of a rubric. Then, two pre-service teachers with "high," "medium," and "low" achievement levels were identified based on the scores obtained from these tests and clinical interviews were conducted with them. As a result of the study, it was determined that the most preferred approach before and after the implementation was SA. However, it was determined that AA and VA, which were less preferred before the implementation, were preferred more after the implementation. In addition, the designed learning environment contributed positively to pre-service teachers' geometry achievement. It was determined that the success of the pre-service teachers in the post-test solutions increased considerably compared to the pre-test. It is thought that it is important to design other courses in the university, for example; Analytic Geometry course should be supported with SA and VA or the Algebra course should be supported with AA and VA and presented to prospective teachers in a new structure.