Self-wrapping is a facile and highly efficient way to realize evenly coating and homogeneous distribution. Ultrasmall antimony (Sb) nanoparticles embedded in three-dimensional (3D) nitrogen-doped porous carbon matrix are fabricated by self-wrapping and controlled growth process with chitosan (CHI) as a self-wrapping precursor. As anode material for sodium-ion battery, the as-obtained Sb/CCHI nanocomposite shows an initial discharge capacity of 403mAhg−1 with Coulombic efficiency of 69.4%, and retains the capacity up to 372mAhg−1 after 100 cycles at a current of 500mAg−1. A reversible capacity of 138mAhg−1 is attained even at a very high current density of 32Ag−1. This unique Sb/CCHI nanocomposite is a potential anode material for high-performance sodium-ion batteries.