Hybrid composite material using a mixture of carbon and sisal natural fibers (Agave Sisalana) and use the matrix PMMA (polymethylmethacrylate) was produced as a biomedical application. Sisal fibers have the advantage of a higher mechanical strength than other natural fibers such as hemp, coconut fiber, and kenaf. While PMMA as the biocompatible matrix has advantages for the human body and a relatively cheap price. Differences in the nature of sisal fibers are hydrophilic and hydrophobic PMMA makes it difficult to achieve a homogeneous dispersion of the fibers in the matrix becomes a significant problem in the manufacture of natural fiber composite materials. The addition of carbon fiber composites is expected to overcome the shortage of sisal / PMMA and worthy to be a substitute for biomedical applications. Alkalization sisal fibers treated with a solution of 6% NaOH for 4 hours. Carbon fiber treated by soaking in a solution of 68% nitric acid for 24 hours, 48 hours, 72 hours and 96 hours. The length of the fiber used ± 6 mm. Comparison of fibers (sisal and carbon) / matrix to be used is 20:80. Composite fabrication method of the random fiber layer using cold press machine manually with a gauge pressure of 120 kg / cm2 at room temperature for 60 minutes. The mechanical tests carried out by the tensile test method which refers to ASTM D638-01. Fault composites were characterized using scanning electron microscopy (SEM) to determine the microstructure of the composite fracture The results showed that the longer carbon fiber on nitric acid can lower the mechanical strength of the composite. Composites with 48 hour immersion variation has the highest mechanical strength is 50.45 MPa and the modulus of elasticity of 1.033 GPa. While the 24-hour immersion variation has the lowest mechanical strength with a value of 45.51 MPa and a modulus of elasticity of 0.844 GPa.