•Two types of bamboo cellulose fiber-based functional materials were fabricated.•Structural materials from cellulose I had the highest tensile strength (571 MPa).•Flexible electrode materials from cellulose II had areal capacitance of 2032 mF cm−2.•Differences between bamboo cellulose I and II were compared. Degradable and sustainable materials are needed to reduce pollution and energy consumption. Bamboo, an inexpensive and abundant resource, can be used to develop such materials. To this end, we demonstrate two types of bamboo-fiber-based functional materials. The first can be used as structural materials with outstanding anti-mildew properties (ultra-high tensile strength: 571 MPa; compressive strength: 191 MPa; surface hardness: 227 MPa) and is produced with long and aligned bamboo cellulose I fibers mixed with epoxy. The second is suitable for electrodes in wearable devices (areal capacitance: 2032 mF cm−2; linear capacitance: 670 F cm−1; energy density: 139.3 µWh cm−2; power density: 80.4 µW cm−2) and uses nickel-coated bamboo cellulose II fibers. The design strategies of bamboo-fiber-based functional materials demonstrated in this study provide new insights for novel degradable and sustainable functional materials.