This study aims to develop mathematics teaching materials based on an open-ended approach to facilitate computational thinking skills in the topic of polyhedrons. The product developed is a printed teaching material, namely the Polyhedron Module based on the Open-Ended Approach. This research uses the Research and Development (RD) method and employs the ADDIE development model, which consists of five stages: Analysis, Design, Development, Implementation, and Evaluation. The test subjects in this study were grade VIII-2 students of MTsN 35 Jakarta and eight validators, consisting of three expert lecturers from the Mathematics Education department and five mathematics teachers from SMP/MTs as practitioners. The results of the study showed that (a) based on expert validation, a score of 0.92 was obtained, indicating that the module is very valid; (b) based on practitioner validation, a score of 0.86 was obtained, and the student response questionnaire yielded a score of 0.82, indicating that the module is very practical; and (c) based on the results of the students' computational thinking skills test, 77.42% of the 31 students achieved scores that met the minimum passing criteria (KKM), with an overall average score of 80, indicating that the module is effective in facilitating computational thinking skills. Therefore, the Polyhedron Module based on the Open-Ended Approach meets the criteria of being valid, practical, and effective.