Key words: geometry teaching learning materials, GeoGebra, engagement, students' achievement The aims of this study are to develop a valid, practical, and effective geometry teaching learning materials using GeoGebra for the seventh grade student. In this study student's handbooks, teacher's instructional guide, and teaching media were developed. Plomp's development procedure is applied to develope teaching learning materials which consist of five stages, namely: (1) preliminary investigation, (2) design, (3) realization/construction, (4) test, evaluation, and revision, and (5) implementation. However, this development was conducted until the forth stage so that the result of the study is in the form of final prototype, which is ready to be implemented in wider area. Based on the results found during the try out, the geometry teaching learning materials being developed is found to be valid, effective, and practical to be used. The result of validation process revealed that the student's handbooks was categorized as a valid, teacher's instructional guide was categorized as a very valid, and media teaching was categorized as a valid. Practicality of teaching learning materials are measured using teacher and students responses. Based on the results, the material turns out to be practical. Effectiveness of teaching learning materials are measured using students' achievement in learning math and students' engagement in learning math. Based on the result of the test it revealed that standard score in math was achieved and students' engagement in learning math was also high. Considering the good result of the try out, it is suggested that the geometry teaching learning materials develoved by using GeoGebra should be implemented in teaching mathematics in the seventh grade. Moreover, teaching learning materials that have been successfully developed in this study, can be used as a guidelines by teachers to develop teaching learning mathematics suitable with the characteristic of the instructional both in term of developing procedures and process to see the quality of the teaching learning materials.