Abstract : Composite reinforced natural fiber is a material that has a good potential to be developed in Indonesia, especially in the automotive field. The mechanical bonding of natural fiber-reinforced composites can be improved by fiber chemical treatment or by using a coupling agent. Chemical treatments, such as alkali treatment, are often used because they are more low cost than the other material. The purpose of this study was to investigate the effect of alkali treatment on the parameters of the composite manufacturing process reinforced bamboo fiber with epoxy matrix. Visual observation was carried out to investigate the fracture modes in the tensile testing process with ASTM D-3039 standard at 0° orientation. The bamboo fiber is immersed in alkaline solution (15% NaOH) for 3, 4 and 5 hours. Furthermore, the fiber is washed using clean water and dried naturally. The matrix used in this study was epoxy bakelite EPR 174. Composites were made using the Hand lay-up method at Vf ≈ 50%. All specimens were curing time at 26°C about 7 hours. Tensile test specimens are made according to the ASTM D-3039 standard. Tensile testing is carried out by using tensile testing machine. The cross-section is investigated to identify the fracture modes. The results showed that the tensile strength of the composite had an optimum value for 3hour fiber treatment, namely 240 MPa with a maximum load of 3600 N, Fiberreinforced composites subjected to 4-hour treatment had the lowest strength, 206 MPa with a maximum load of 3100 N. Composite fracture cross-section fiber reinforced with 15% alkali treatment 3, 4 and 5 hours. Visual failure mode was observed according to the ASTM D-3039 standard and could be classified as a type of lateral, splitting and angle fracture that occurred in this study. Composite reinforced natural fiber is a material that has a good potential to be developed in Indonesia, especially in the automotive field. The mechanical bonding of natural fiber-reinforced composites can be improved by fiber chemical treatment or by using a coupling agent. Chemical treatments, such as alkali treatment, are often used because they are more low cost than the other material. The purpose of this study was to investigate the effect of alkali treatment on the parameters of the composite manufacturing process reinforced bamboo fiber with epoxy matrix. Visual observation was carried out to investigate the fracture modes in the tensile testing process with ASTM D-3039 standard at 0° orientation. The bamboo fiber is immersed in alkaline solution (15% NaOH) for 3, 4 and 5 hours. Furthermore, the fiber is washed using clean water and dried naturally. The matrix used in this study was epoxy bakelite EPR 174. Composites were made using the Hand lay-up method at Vf ≈ 50%. All specimens were curing time at 26°C about 7 hours. Tensile test specimens are made according to the ASTM D-3039 standard. Tensile testing is carried out by using tensile testing machine. The cross-section is investigated to identify the fracture modes. The results showed that the tensile strength of the composite had an optimum value for 3hour fiber treatment, namely 240 MPa with a maximum load of 3600 N, Fiberreinforced composites subjected to 4-hour treatment had the lowest strength, 206 MPa with a maximum load of 3100 N. Composite fracture cross-section fiber reinforced with 15% alkali treatment 3, 4 and 5 hours. Visual failure mode was observed according to the ASTM D-3039 standard and could be classified as a type of lateral, splitting and angle fracture that occurred in this study.