Sugarcane bagasse is a plantation waste containing cellulose fiber, which can be used as a composite material. Natural fiber composites with epoxy matrices have several advantages, including good mechanical properties. The addition of carbon nanotubes (CNT) to composites known through many studies can improve mechanical properties. Alkali treatment with NaOH is carried out on the fiber to remove impurities on the surface of the fiber and activate hydroxyl groups from the fiber. Mild acid oxidation is carried out on CNT using HNO3 and H2O2 to functionalize CNT to become CNT-OH. The silane coupling agent (GLYMO) treatment was performed on fiber and CNT to improve compatibility with the matrix. In this study, the addition of carbon nanotubes on bagasse fiber composites (bagasse) with the epoxy matrix as much as 0.5%, 1% and 1.5% of the weight of the matrix used. FTIR result proves the success of the alkali, mild acid oxidation and silane coupling agent treatment by showing hydroxyl, carboxyl and silanol groups. Besides, Uv-Vis Spectroscopy also showed the success of the CNT functionalization process by increasing CNT solubility dispersion. The bending test results obtained from the study were to increase the flexural strength of composites by 150.65%, 87.61%, and 72.73% in the addition of CNT 0.5%, 1% and 1.5% by weight. It can be concluded that the addition of CNT will increase the flexural strength of the CNT to the optimum point of CNT addition by 0.5% by weight. Further addition will reduce the flexural strength due to CNT agglomeration. The composite results obtained can be utilized in the automotive industry for car interior materials.