eng Science and Education Publishing American Journal of Educational Research 2327-6150 2019-01-08 7 1 24 32 10.12691/education-7-1-5 EDUCATION2019715 article Mahdalena Elma Sari 1 M. Amin Fauzi 1 Faiz Ahyaningsih mahdalena.elmasari29@gmail.com 1 Postgraduate Program in Mathematics Education, Medan State University, Indonesia This study aims to: 1) Develop teaching materials based on a valid metacognition approach to improve students' understanding of mathematical concepts; 2) Developing teaching materials based on a practical metacognition approach to improve the ability to understand students' mathematical concepts; 3) Develop teaching materials based on an effective metacognition approach; 4) To analyze the increased ability to understand students' mathematical concepts by using teaching materials based on metacognition approaches. This research is a development research using a 4-D development model, the teaching materials developed from this study are: Learning Implementation Plans, Teacher Books, Student Books, Student Worksheets, And Tests Ability To Understand Mathematical Concepts. From the results of trial I and trial II, it was obtained: 1) Teaching materials based on the metacognition approach developed have met valid criteria from several criteria; 2) Teaching materials based on the metacognition approach developed have met Practical criteria from several criteria; 3) Teaching materials based on the metacognition approach developed have met the effective criteria of several criteria; 4) there is an increase in the ability to understand students' mathematical concepts by using instructional materials based on the metacognition approach developed, in the trial I obtained an average score of pretest 54.66% and posttest score 73.86%, and in the second trial with an average pretest score of 57.87% and posttest score of 78.4%. http://pubs.sciepub.com/education/7/1/5/education-7-1-5.pdf teaching material development metacognition approach 4-D model ability to understand mathematical concepts