Despite high porosity, deer antlers exhibit high strength and toughness from synergistic hierarchical structures. MXene fibers offer promising applications but suffer from poor mechanical properties due to internal voids and weak interfaces. Conventional strengthening removes voids and enhances interlayer interactions, but yields rigid, brittle fibers. Here, we tackle this trade-off by constructing strong and slidable double-interfaces that can cooperate with internal micropores in MXene fibers to mimic the delicate structure of deer antlers. These voids, typically considered defects, instead enhance load-bearing and energy dissipation. At an optimal porosity of ~21%, the MXene fibers achieve high tensile strength, ductility, and toughness of 1060.1 ± 33.5 MPa, 34.2 ± 1.8%, and 136.1 ± 6.5 MJ m^-3, respectively. Notably, this MXene-matrixed fiber shows elasticity and high durability and is even softer than polymer fibers, while maintaining an electrical conductivity of over 10500 S cm^-1 after being coated with silver nanowires. This biomimetic approach enables robust, multifunctional fibers for smart textiles.