Penelitian ini bertujuan untuk mengetahui ada tidaknya pengaruh kemampuan komunikasi matematis terhadap prestasi belajar matematika siswa kelas ix smp frater don bosco tarakan. jenis penelitian yang digunakan dalam penelitian ini adalah survei. penelitian ini dilaksanakan pada siswa kelas ix smp semester ganjil pada tahun pembelajaran 2021/2022 di smp frater don bosco tarakan. metode pengumpulan data menggunakan instrumen tes dan dokumentasi nilai pts (penilaian tengah semester). populasi dalam penelitian ini adalah seluruh siswa kelas ix smp frater don bosco tarakan. sampel dalam penelitian ini sebanyak 43 siswa yang diambil menggunakan teknik sampling jenuh hasil penelitian menunjukkan bahwa terdapat pengaruh kemampuan komunikasi matematis terhadap prestasi belajar matematika siswa kelas ix smp frater don bosco tarakan, dengan persamaan regresi Ŷ = 50.631 + 0.527x. berdasarkan analisis hasil uji t, diperoleh nilai sebesar 3.284 ≥ sebesar 2,08108 maka ditolak dan diterima. sehingga dapat disimpulkan bahwa terdapat pengaruh antara kemampuan komunikasi matematis terhadap prestasi belajar matematika siswa kelas ix smp frater don bosco tarakan. kata kunci: kemampuan komunikasi matematis, prestasi belajar

This study sought to determine whether mathematics learning achievement of class ix students at frater don bosco junior high school tarakan was influenced by their ability to communicate mathematically. this study used survey research as its methodology. this study was carried out in the class ix of frater don bosco junior high school tarakan throughout the odd semesters in the academic year 2021 2022. test instruments and pts (middle semester assessment) scores were recorded as data collection methods. the population in this study were all grade ix students of frater don bosco junior high school tarakan. the sample in this study was 43 students who were taken using the saturated sampling technique. the results showed that there was an influence of mathematical communication skills on mathematics learning achievement of class ix students of frater don bosco junior high school tarakan, with the regression equation = 50,631 +0.527x. according to the t-test results, ho was rejected and h1 was approved since the t-count value was 3.284 and the t-table value was 2,08108. it was concluded that there was an effect of mathematical communication skills on mathematics learning achievement of class ix students of frater don bosco junior high school tarakan. keywords: mathematical communication ability, learning achievement