Abstrak: Penelitian ini bertujuan untuk meningkatkan penguasaan konsep geometri dan pengukuran mata pelajaran Matematika siswa kelas IV SD. Penelitian ini termasuk dalam Penelitian Tindakan Kelas (PTK) menurut teori C. Kemmis dan Mc. Taggart yang telah dilaksanakan selama dua siklus. Subjek penelitian ini adalah siswa kelas IV SD sebanyak 25 orang. Instrumen yang digunakan yaitu lembar observasi guru, siswa dan penguasaan konsep siswa. Berdasarkan hasil penelitian persentase pencapaian penguasaan konsep siswa mengalami peningkatan secara bertahap, yakni pada pra siklus sebesar 12%,  siklus I menjadi 40%, siklus II meningkat menjadi 84%. Dengan demikian, penguasaan konsep yang diharapkan telah mencapai indikator keberhasilan dan dapat disimpulkan bahwa penerapan teori belajar Bruner dapat meningkatkan penguasaan konsep geometri dan pengukuran.Abstract: This research aims at increasing the comprehension of geometry and measurement concepts of the fourth graders in Public Elementary School. Based on the definition made by C. Kemmis and Mc. Taggart, this research can be classified as Classroom Action Research (CAR) which consists of two cycles. The research subjects were the fourth graders in Public Elementary School are 25 students. The results showed that the students' comprehensions were gradually increasing. During the pre-cycle, the percentage was 12% and it increased to 40% at the end of first cycle. It was then increased to 84% at the end of second cycle. Therefore, it can be concluded that the implementation of Bruner's learning theory can help increase student's comprehension of geometry and measurement concepts.