Abstrak: Penelitian ini bertujuan untuk mengetahui pengaruh pendekatan matematika realistik terhadap prestasi belajar matematika dan sikap bersahabat di kelas IV Sekolah Dasar. Penelitian ini merupakan penelitian quasi eksperimental dengan desain Nonequivalent (Pretest-Posttest) Control Group Design. Sampel penelitian ini adalah siswa kelas IV SD sebanyak 42 siswa yang terbagi menjadi 20 siswa sebagai kelompok eksperimen dan 22 siswa sebagai kelompok kontrol. Penentuan sampel menggunakan cluster random sampling. Teknik pengambilan data dilakukan dengan instrumen prestasi belajar siswa melalui pretest dan posttest sedangkan instrumen sikap bersahabat didapatkan dengan angket menggunakan skala Likert. Pengujian hipotesis menggunakan uji-t pihak kanan, dimana t-hitung lebih besar dari t-tabel sehingga Ho ditolak dan Ha diterima. Hasil penelitian menunjukkan bahwa: (1) terdapat pengaruh antara pendekatan matematika realistik terhadap prestasi belajar siswa dengan t-hitung = 3,399 ≥ t-tabel = 1,684; (2) terdapat pengaruh antara pendekatan matematika realistik terhadap sikap bersahabat siswa dengan t-hitung = 2,160 ≥ t-tabel = 1,684.Abstract: This research aimed to find out the effect of realistic mathematics approach towards the students' learning achievement and friendly behavior on the fourth grade of Elementary School. This was a quasi-experimental research with Nonequivalent (pre-test and post-test) Control Group Design. The samples of this research were 42 fourth graders of Elementary School taken from two classes consisting of 20 students of the experiment class and 22 students of the control. The data of students'learning achievement were collected using pre-test and post-test, while the data of students' friendly behavior were collected using a questionnaire of Likert scale. To test the hypothesis of this study using the right t-test, where t-count was bigger than t-table so Ho will be rejected and Ha will be accepted. The results showed that: (1) there was an effect between realistic mathematics approach and the students' learning achievement with t-count = 3.399 ≥ t-table = 1.684; (2) there was an effect between realistic mathematics approach and students' friendly behavior with t-count = 2.160 ≥ t-table = 1.684.