The paper folding method for teaching mathematics is used as a concrete material in primary and secondary schools to explore concepts, primarily geometry, and understand the relationship between these concepts. The overarching definitions expressing the relations of the quadrilaterals are ignored when teaching plane geometry. This research is differentiated from other studies in creating original content by approaching origami and quadrilaterals conceptually. In this study, pre-service teachers will be provided to rethink the conceptual relationship between quadrilaterals with origami. The primary purpose is to determine the effect of paper folding activities on pre-service teachers' concept images of quadrilaterals. A quantitative research method, a single group pre-test-post-test design, will be used to achieve this aim. The study data were collected with "Concept Image Questions" and "Geometry Attitude Scale." As a result of the data analysis, it was seen that while the pre-test was directed to the exclusionary definitions, the concept images of the inclusive definitions intensified in the post-test. In addition, no significant change was observed in the geometry attitudes of pre-service teachers. At the end of the study, it was concluded that the application of origami activities would enable pre-service teachers to express comprehensive definitions of quadrilaterals and to deal with the relations of quadrilaterals with each other in a conceptual dimension. Thus, students' awareness of plane geometry subjects taught in schools will increase indirectly.