Nanofiller composite resin has small filler size which enhances its properties. However, these properties could decrease due to several factors. Acidic liquid such as coffee could reduce the hardness of composite resin. This study was aimed to analyze the effect of robusta and arabica coffee immersion on the hardness of nanofiller composite resin. A total of 27 composite resin samples were used and then were polished by using a soflex disc for 30 seconds on each roughness level. Samples were then divided into three groups, as follows: the control group with artificial saliva and the treatment groups with robusta coffee and arabica coffee. The composite resin molds were immersed in the three groups for 5 days. After five days of immersion, the hardness of the sample was tested by using a Vickers hardness tester. Artificial saliva as the control group had the highest mean hardness value of 112.98±8.67 VHN, followed by robusta coffee, and then by arabica coffee. The One Way Anova and post hoc LSD test showed that there were significant differences in all groups (p<0.05) except for the two treatment groups, namely robusta and arabica coffee groups which did not show any significant difference in the resin hardness (p>0.05). In conclusion, robusta and arabica coffee affect the hardness of the nanofiller composite resin, but there is no significant difference in the hardness between the robusta and arabica coffee groups.Keywords: composite resin hardness, nanofiller, robusta coffee, arabica coffee Abstrak: Resin komposit nanofiller memiliki ukuran filler kecil yang dapat meningkatkan fungsinya namun fungsi tersebut dapat menurun oleh beberapa hal. Cairan asam yang dikonsumsi seperti kopi dapat menurunkan kekerasan resin komposit. Penelitian ini bertujuan untuk mengetahui pengaruh perendaman kopi robusta dan arabika terhadap kekerasan resin komposit nanofiller. Sampel resin komposit yang digunakan sebanyak 27 buah dan dilanjutkan dengan pemolesan menggunakan soflex disc selama 30 detik setiap tingkat kekasarannya. Sampel kemudian dibagi dalam tiga kelompok, yaitu kelompok kontrol dengan saliva buatan dan dua kelompok perlakuan dengan kopi robusta dan arabika. Sebanyak 27 buah resin komposit direndam ke dalam tiga kelompok tersebut selama lima hari kemudian diuji kekerasannya dengan vickers hardness tester. Saliva buatan sebagai kelompok kontrol memiliki nilai rerata kekerasan tertinggi sebesar 112,98±8,67 VHN, diikuti kopi robusta, dan nilai terendah yaitu kopi arabika. Hasil uji One Way Anova dan post hoc LSD menunjukkan terdapat perbedaan bermakna pada semua kelompok (p<0,05) kecuali pada kedua kelompok perlakuan yaitu antara kopi robusta dan arabika tidak menunjukkan adanya perbedaan kekerasan yang bermakna (p>0,05). Simpulan penelitian ini ialah kopi robusta dan arabika memengaruhi kekerasan resin komposit nanofiller namun tidak terdapat perbedaan kekerasan antara keduanya.Kata kunci: kekerasan resin komposit, nanofiller, kopi robusta, kopi arabika