Mathematical representation includes the process of transforming problems or ideas into new forms, including changing pictures or physical models into symbols, words, or sentences that can facilitate students in solving mathematical problems. Pythagorean Theorem material is widely used in analytic geometry, so this material becomes important for students in understanding geometric concepts which makes this material a prerequisite material. Therefore, the purpose of this research is to describe the ability of students' mathematical representations in solving mathematical problems in the Pythagorean theorem material. The research method used in this study was qualitative with the subject of the research being class IX students at one of the junior high schools in Bandung City, totaling 28 people. From the research that has been done, it is concluded that the description of the most dominant mathematical representation ability lies in the low ability of students to present mathematical ideas contained in the problem in the form of image representation so that students are not facilitated in solving a problem presented. In addition, there are still students who experience errors in solving problems involving arithmetic symbols (symbolic representation). In answering questions related to contextual problems, there are still students who have not been able to optimally use representations to model and interpret mathematical phenomena. [For the full proceedings, see ED652261.]