Abstrak: Penelitian ini bertujuan untuk mendeskripsikan kemampuan number sense mahasiswa Program Studi PGMI FTK UIN Mataram. Penelitian ini merupakan penelitian kualitatif. Subjek penelitian adalah mahasiswa PGMI konsentrasi matematika. Prosedur pemilihan subjek menggunakan purposive sampling. Pengumpulan data dilakukan dengan cara think aloud method. Teknik analisis data dilakukan dengan cara: (1) mengelompokkan subjek berdasarkan kemampuan awal matematika tinggi, sedang, dan rendah: , (2) menyajikan data, dan (3) menyimpulkan kemampuan number sense. Hasil penelitian menunjukkan bahwa mahasiswa pada kemampuan awal tinggi sudah menguasai konsep dasar dari number sense. Pada kemampuan awal sedang dan rendah belum memahami dan menguasai sepenuhnya konsep dasar number sense.Abstract: The purpose of this research was to describe the number sense ability of student at Study Program of PGMI FTK UIN Mataram. This research was a qualitative research. The subject were the students of mathematics concentration. Subject selection procedure was done by purposive sampling method. Techniques of data analysis were done by: (1) classifying subjects based on high, medium, and low mathematics ability. (2) presenting the data, and (3) summarizing the number sense capabilities. Based on the research, students in the high mathematic ability have mastered the basic concept of the number sense. The student at middle and low mathematics ability have not been able to fully understand and master the basic concept of number sense.