Natural fibers as composite reinforcing materials have attracted the interest of researchers around the world because of its superior properties such as specific strength, light weight, low prices, good mechanical properties, non-abrasive and biodegradable. Composites have been widely used for various applications in human life, including the application of biomedical devices. However, natural fiber composites have lower mechanical strength compared to synthetic fiber composites. The purpose of this study is to make high density polyethylene (HDPE) hybrid composites reinforced sisal fiber, abaca fiber and carbon fiber as biomedical device materials, and to know the mechanical properties of bending and physical properties of water absorption hybrid composites with variations in the volume fraction of hybrid fibers. Hybrid composites were fabricated using the hand lay-up method in a hot press machine at 140˚C and 1.4498 MPa for 60 minutes with a matrix/filler composition of 80/20% by weight. Sisal and abaca fibers are alkalized by soaking each fiber in 6% NaOH for 36 hours, while carbon fiber is treated with liquid nitrogen for 10 minutes. Variations were made on the ratio of volume fraction of abaca/sisal/carbon hybrid fibers, that is (3: 0: 1), (3: 3: 2), and (0: 3: 1). Bending tests with ASTM D790 and water absorption tests with ASTM D570 were carried out on all hybrid composite specimens. The characterization of the bending test crack structure is carried out from the side of the cross section using an optical microscope. The results showed that the highest strength (45.93 MPa) and elastic modulus (3.024 GPa) of abaca/sisal/carbon/HDPE composites were achieved by variations in sisal/carbon hybrid composites (3:1) and the percentage of water absorption and thickness increase is 9.28% and 3.91%. These results are related to the more even distribution of natural and synthetic fibers.